Poly(glycolic acid) for containers and films with reduced gas permeability

ABSTRACT

Compositions of high molecular weight poly(hydroxy acid) polymer having good thermal stability and a weight average molecular weight of &gt;100,000 by GPC. The compositions include one or more chain-terminator compounds/impurities which may be incorporated into the polymer and rendered harmless by the presence of appropriate amounts of bi-functional and multi-functional polymerization initiators. A process including first mixing glycolic acid and/or lactic acid (with chain-terminators), and a diol or di-acid initiator, and at least one multifunctional initiator to form a liquid monomer mixture in an agitated polycondensation reactor. Next, polycondensing to form a liquid reaction mixture comprising a pre-polymer having a weight average molecular weight of &gt;10,000 by GPC, and greater than 80% by mole hydroxyl or carboxyl end-group termination, then crystallizing to form a first solid reaction mixture. Then, solid state polycondensing the solid reaction mixture to form a solid reaction mixture having a moisture level less than 50 ppm by weight. Then, mixing the solid reaction mixture with an appropriate reactive coupling agent in a melting and mixing extruder to couple and form the reaction mixture and form the final poly(hydroxy acid) polymer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is related to “Process for Making Poly(glycolicacid) for Containers and Films with Reduced Gas Permeability” Ser. No.16/728,123 US filed concurrently with the present application andincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to compositions and processes for improving gasharrier properties in a rigid polyester container or film wall,especially carbonated soft drink (CSD) bottles and flexible packagingfor oxygen sensitive products.

Description of the Background

A gas barrier may be passive type, where there is a physical encumbranceto transit of diffusing gas molecules, or an active type, where specialadditives hind, react, scavenge, or entrap the diffusing gas moleculevia a chemical reaction. Increasing polymer density to reduce molecularfree volume mechanically falls under passive type, where the closelypacked molecules with crystalline structure are relatively impervious toa diffusing gas molecule and gas molecule diffusion is greater withinareas filled by less dense, less ordered, relatively open amorphouspolymer structures.

Polyethylene terephthalate and co-polyesters of polyethyleneterephthalate (polyethylene terephthalate and co-polyesters ofpolyethylene terephthalate are hereinafter referred to as PET) arepreferred packaging materials for multi-serve and single-serve CSD andstill beverages and food stuffs. Beverages commonly packaged with PETinclude carbonated soft drinks, juice, juice drinks, water, flavoredwater (still and carbonated), hydration drinks, teas, new age drinks,milk and milk drinks, etc. PET has a number of properties that make itsuse for packaging such drinks favorable. For example, PET has mechanicalstrength, e.g. drop impact strength, burst strength and thermalexpansion when biaxially oriented, and gas barrier resistance, all ofwhich make PET desirable as a packaging material for beverage containersand provide container design freedom.

Polyester resins such as poly(ethylene terephthalate) (PET),poly(butylene terephthalate) (PBT), poly(ethylene naphthalate) (PEN),poly(tri-methylene terephthalate) (PTT), and poly(tri-methylenenaphthalate) (PTN), have conventionally been used as resins in themanufacture of food and beverage containers such as beverage bottles.Some resins such as PTT, PEN and PTN are used mainly for specializedpackaging applications because these resins are significantly moreexpensive to manufacture than, for example, poly(ethylene terephthalate)resins. Properties such as flexibility, good impact resistance, andtransparency, together with good melt processability, permit polyesterresins to be widely used for making food and beverage containers. PETresins are among the most widely recycled plastics.

An important property of any polymer resin such as a PET resin used infood container or beverage container applications is the resin's abilityto resist the ingress and egress of gases, such as oxygen (O₂) andcarbon dioxide (CO₂), through the container's walls. Containers forcarbonated beverages may be especially susceptible to the egress ofgases such as carbon dioxide which are normally present in carbonatedsoft drinks. Usually, a carbonated soft drink will contain about 4volumes of dissolved carbon dioxide gas per volume of the liquidcarbonated soft drink. Other beverages such as beer typically haveapproximately 1.5 to 3.0 volumes of total dissolved carbon dioxide. Ifthe resin used to form a beverage container permits carbon dioxide toescape, the product delivered to the consumer may be of unacceptablequality (e.g. “flat”) if stored too long. In food containerapplications, it is important that the container material resists theingress of oxygen. Oxygen in contact with a food substance may lead tocolor changes and oxidation that accelerates spoilage of the foodproduct.

PET and the other aforementioned polyesters do not meet all of the gasbarrier requirements for small size single serve drink containers (e.g.,containers for serving sizes of less than 24 oz.). To be acceptable forsingle serve drink containers, a packaging container must be able toprovide retention of CO₂ for carbonated soft drinks and exclusion of O₂for oxygen sensitive drinks or in the case of beer, both CO₂ egress andO₂ ingress. Large, multi-serve containers made from PET generally meetthe packaging requirements with respect to CO2 retention and/or O₂exclusion and are thus able to maintain the quality of the productreaching the consumer after filling, shipping, storage and purchase.Similar performance in single-serve drink containers is desirable tomeet consumer demand for smaller serving size to provide convenience,portability, and portion control. Beverage brand companies havelong-standing market needs for distribution of single-serve plasticcontainers in multi-packs, e.g. 12- and 24-packs, with improvedgas-barrier-related shelf life. This market segment is served primarilyby aluminum cans due to shorter shelf life of single serve plasticcontainers.

Different technologies have been developed to enhance the gas barrierproperties of PET packaging materials. For example, PET containers maybe coated with an internal and/or external coating to improve gasbarrier performance. Other methods for improving gas barrier performanceof PET containers include the use polymer blends, co-monomersubstitution, and multi-layers containers.

Certain technologies to improve gas barrier package performance, such asadditional coating(s) or layer(s), typically require use ofmanufacturing equipment that is substantially more complicated, requiresa greater initial capital outlay, and greater operating expenses.Although initially these economic demands may seem unfavorable, once theequipment investment has been committed the use of such technologies canbe economically beneficial versus the alternatives of shortershelf-life, greater product spoilage, and/or heavier packages. And ifthe coating/layering material(s) can be removed effectively from apredominantly PET container, then the recyclability of the container canbe enhanced to be equivalent to that of a 100% PET container, but withthe functional benefit of improved gas barrier.

Polymer blends are typically made from a mixture of a PET blended withanother polyester material such as polyethylene naphthalate (PEN),polyethylene isophthalate (PEI) or other types of polymers such aspolyamides (e.g., nylon). PET can also be modified by using co-monomersthat are directly bonded to the polyester polymer chain. Co-acid monomersuch as isophthalate-, naphthalate- and/or resorcinol-based co-diols mayimprove gas barrier performance. However, in order for a PET copolymerto achieve even moderate improvement in gas barrier performance, e.g.,preferably a 1.2× to 2× or greater barrier improvement factor (e.g., animprovement in gas barrier resistance of at least 20% to 100%), pure PETpolymer typically requires the addition of 10-20 weight % or mole % of abeneficial co-monomer(s). This can substantially increase the PET resincost and/or the complexity of the process used to manufacture the PETand bottles made from, as well as create problems with other physicalproperties of the PET (e.g. clarity, color, or strength).

Crystallinity is an important factor in gas permeability of a polymerbecause the polymer crystals are relatively impermeable as compared withthe amorphous regions within the polymer bulk. Thus, a permeant gasmolecule must preferentially seek out amorphous regions in order torapidly penetrate a polymer. A lower degree of crystallinity results inhigher gas permeability. The polymer state with the highest degree ofcrystallinity provides the lowest gas permeation, thus a better gasbarrier. Increasing the molecular order, packing, and crystallinity ofgas barrier polymers increases density and decreases gas permeability.Thus, incorporating a polymer substantially more crystalline than PETcan improve the gas barrier performance of a coated or multi-layercontainer predominantly comprised of PET.

Free volume, which exists in glassy polymers such as PET which have aglass transition temperature (T_(g)) that is substantially higher thanambient temperature, may affect a polymer film's ability to resist thepassage of gases. Free volume is considered to be representative ofunrelaxed volume of the polymer and represent the “open” spacesremaining in a polymer matrix that occur when a polymer becomes glassyand segmental mobility of the main polymer chain is “frozen.”

Free volume in a glassy polymer may consist of two independentcomponents, one of which is affected by annealing and the other byanti-plasticization. Anti-plasticization may occur when small amounts ofcertain plasticizers are added to certain glassy polymers.Anti-plasticization is only observed in the temperature regions belowthe glass transition temperature (T_(g)) of the polymer.Anti-plasticization arises from an interaction between the polymer andthe plasticizer molecules and decreases the molecular mobility of thepolymer and plasticizer. Anti-plasticizers are compounds which arecompatible with PET resins and which contain one or more polar atomssuch as oxygen, nitrogen, etc. and have at least one aromatic ring withor without a non-bridged ring.

Polyethylene isophthalate (PEI) made from 100% purified isophthalic acidhas high-barrier properties and has a much lower CO₂ permeability thanamorphous or crystalline PET. This can be considered to be a result ofdifferences in the dynamic conformational flexibility between PEI andPET. In PEI, the meta-attachment of ethylene glycol units prevents theflipping of phenyl rings in the PEI polymer. Amorphous PET is able tofreely flip its phenyl rings without changing its overall conformation,i.e., without moving or changing the conformation of the PET backbone.The free flipping of phenyl rings in PET may provide an effectivepathway for gases to permeate through bottle side walls/films/sheets andmay make PET more permeable to gases than PEI. In practice, PEI chipsare completely amorphous and special drying procedures are needed toprevent stickiness. PEI will soften and agglomerate above T_(g) (˜60°C.). PEI should be dried at less than 50° C., preferably under vacuum.To resolve special drying conditions for chips and provide adequatecrystallinity for chips, only a narrow range (˜10-20%) of IPA can bepresent in the polymer backbone to offset the large use of expensiveorganic diluents. Otherwise, additional separate material dryers arerequired for this option.

The addition of a monomeric or polymeric organic molecule in smallamounts to a base polymer (e.g., a polyester or co-polyester such asPET, PEI etc.) can result in anti-plasticization of the polymer wherebyits resistance to gas permeability can improve. For example, theinclusion of tri-cresyl phosphate in polyphenylene oxide has beendisclosed to lower the sorption of carbon dioxide and hence reduce theresin's permeability to carbon dioxide [Maeda, Y. and D. R. Paul, J.Polym. Sci., Part B: Polym. Phys. 25, 981-1003 (1987)]. Polymericanti-plasticization of polycarbonate with polycaprolactone has also beenreported [Siegmann, A., Polym. Eng. Sci., 1994].

The addition of low molecular weight compounds to PET is a technologythat has been used to improve gas barrier performance in PET polymerfilms, bottles and containers for packaging applications. Such lowmolecular weight compounds are typically referred to as molecularbarrier additives. When present as a mixture with PET, low molecularweight compounds occupy free volume within the polymer matrix and mayinteract with different polymer chains through polar groups on the lowmolecular weight compound and the polymer chains. Robeson and Faucherdisclosed in J. Polymer Science (1969) that the presence of certain lowmolecular weight compounds in polymeric materials such as polycarbonate,polyvinyl chloride, poly(phenylene oxide), and poly(ethylene oxide) maylead to an increase in the modulus of the polymeric material andconcurrently reduce gas permeability. These effects were thought to bedue to an anti-plasticization effect. Anti-plasticization is an effectwhereby the chains of polymers in a polymeric matrix and/orpolymer-containing composition have secondary interactions with othermolecules, e.g., with a further compound or with other polymer moleculespresent in the matrix.

Ruiz-Trevino and Paul disclosed that certain low molecular weightcompounds may function to improve the gas barrier properties ofpolysulfone membranes and/or films. It was speculated that a mechanismthat results in interaction of the polar groups of the compounds withthe polar groups of the polysulfones reduces the free volume of thepolysulfone compositions, for example by bringing the polysulfone chainscloser to one another. The resulting composition thereby providedreduced the gas permeability. The low molecular weight compounds werepresent in amounts from 10 to 30% by weight.

U.S. Pat. No. 6,489,386 discloses compositions that include one or morePET polymers and methyl-4-hydroxybenzoate and/or a compound relatedthereto. The addition of an ester-containing additive was found toaffect gas barrier properties.

U.S. 2006/0275568 discloses the use of di-alkyl esters of aromaticdi-acids as additives for PET compositions. Improved gas barrierperformance was obtained without any significant change in the intrinsicviscosity (IV) of the composition when certain catalysts such as Ti- andAl-containing catalysts were used and the compositions were otherwisefree of catalyst metals such as Sb, Co, Ca, etc.

Inherent viscosity may be measured according to ASTM D4603-96 (e.g., IhVmeasured at 30° C. with 0.5% concentration in a 60/40phenol/1,1,2,2-tetrachloroethane solution by means of a glass capillaryviscometer). The IV (intrinsic viscosity) of a polymer, [□], is thelimiting value of the inherent viscosity (IhV) at infinite dilution ofthe polymer. The IV (or IhV) units are in dL/g.

U.S. 2005/0221036 discloses the use of naphthalene di-hydroxides in PETcompositions. The inclusion of compounds of formula. HO-AR-OH, where theAR group is a naphthalene-containing group, was shown to reduce the gaspermeability of the polymer compositions.

U.S. 2007/0082156 discloses the use of a purine derivative, particularlya purine dione such as caffeine as an additive to PET to improve theoxygen and carbon dioxide barrier properties of the resulting beveragecontainer.

Additional gas barrier references include U.S. Pat. Nos. 6,090,460,6,461,697, 6,602,568, 6,808,820, 8,545,952 B2, U.S. 2005/0009976, U.S.2011/0036850, and U.S. 2017/027018.

Thermoplastic PET resins are used in the packaging industry for rigid,semi-rigid, and flexible film containers. Commonly used rigid packagesare containers for carbonated and non-carbonated beverages and food aswell as non-food liquids, such as shampoos and household detergents.These containers can be made by a two-step process. In the first step apreform is produced by injection molding, and in the next step thepreform is reheated and biaxially stretched and blown to give finalcontainer shape, size, and integrity with desirable thermo-mechanicalproperties.

As a pre-conditioning step prior to the injection molding process, thepolyester resin(s), of similar species or physical mixtures have to bedried and fed from a drying hopper. They are then conveyed and melted byextrusion screw and injected under pressure into a mold. The mold mayhave one or more preform cavities to make a one or several preforms in asingle cycle. The molded preform may have a single- or multi-layerstructure type. In a single-layer application, the matrix composition isone polyester resin throughout the preform bulk.

In a multi-layer application, two or more different resins may be fedindependent of each other to create a multilayered preform structure.For example, a three-layer bottle may have an ABA structure, where amiddle layer of resin B is sandwiched between two structural layers ofresin A on either side. The B layer is often a thin section of the wall,generally about 2% to 20% of the total preform wall thickness. Themulti-layer bottles allow for a specialized resin, often with highercost and/or with reduced compatibility with the PET structural layers,to be isolated in a specific location within the container. The finalstructure is ABA, the co-injection injection molding sequence is A, AB,A (where A is injected first, while A is being injected, B isintroduced, then B is stopped and A continues until the final preform ispacked out).

The timing sequence and mold temperatures can be adjusted to positionthe specialized B layer in the center of the preform or preferentiallyto the inside or outside of the preform wall. The sequence can also bemanaged to position the specialize B layer so that it only falls withinthe regions of the preforms that will eventually reheated and stretchblow molded. The advantage of this is to minimize or eliminate thespecialize material from being in the thicker amorphous regions of thethread finish and base pushup regions that do not get stretched duringthe blowing process. This also allows for the total encapsulation of thespecialized B polymer. A second option is to create a 5-layer structureABABA via a sequential injection molding sequence A-B-A. In this case, Ais injected first, and then stopped, B is injected next and thenstopped, and then A is injected last packing out the preform. Thiscreates two thin B layers due to the Fountain Flow filling of injectionmolding cavities.

In the blow molding step, preforms are loaded on a conveyor and arepassed in front of infrared (IR) heating lamps to heat the preformtypically 10-20° C. above the polymer glass transition temperature(T_(g)) prior to the stretching and blowing steps. The preform isthicker and shorter than the final container wall to account for theself-leveling of the polymer and the resulting axial and hoop stretchratios (blow up ratio BUR) of the final container shape. To reheat thepreform uniformly, typically, a low concentration of IR absorbingspecies, called reheat or fast heat up additive, are added to thepolymer to improve the absorption of IR-radiation by the polyesterpreform and subsequently conduct heat into the surrounding preform wallsection.

The preform reheating process is inefficient. The IR selectivewave-length lamps radiate energy to penetrate the PET preform, but alsorequire air circulation to cool the preform surfaces during thereheating process due to the low heat conductivity of the PET. Notcooling the preform surface can result in overheating and the onset ofcrystallization of the surfaces rendering the container opaque or hazy.

On application side, the stretch blow molded PET containers offerconvenience of meeting physical and other application requirements suchas dimensional stability, clarity, cost, and recyclability. However,unmodified PET containers have relatively high gas permeability and mayallow diffusion of gas molecules in both directions across the containerwall. In a typical CSD package, the container is pressurized to inexcess of 4 volumes of CO₂, which over a span of several weeks will beabsorbed into and diffused through the container sidewalls, lowering thecarbonation level below the minimum that is known to affect the tastedof the product. In the case of some food type products, e.g., ketchupbottles, oxygen from the ambient air will ingress into the container andcan alter the taste and color of the product. In either case, absorptionand diffusion of gas molecules through the walls of the PET plasticcontainer may limit the product's shelf life.

CSD product shelf life is adversely affected for smaller packages whichhave higher ratio of surface area to volume and therefore sufferrelatively higher gas-permeation carbonation loss than larger volumecontainers.

The shelf life for these containers can be increased by improving gasbarrier properties of the plastic container. A barrier layer within acontainer may be ‘passive’ or ‘active’ or a combination of both.

With a passive barrier, gas diffusion may be retarded by combining PETwith more impervious copolymers or by increasing the diffusive pathlength by increasing tortuosity of a less resistive pathway. MXD6 nylonand EVOH are just two examples of barrier type polymers that arecommonly used to accomplish the former, while exfoliated clays may beused for the latter. A passive gas barrier retards diffusion of CO₂and/or O₂. However, it does not stop the flux of gas molecules in or outof the container wall.

An active gas barrier, e.g. an oxygen scavenging molecule, involvesreaction and subsequent immobilization of gas molecules with a polymericor other compound, typically in presence of a catalyst. Over time,continued oxygen ingress can exhaust the reactive species. Therefore,active barrier systems can attain longer shelf life if the underlyingpermeability of the base polymer container is also enhanced to retardgas diffusion.

A straightforward way of improving gas barrier is to thicken thecontainer wall, since greater thickness can increase the diffusive pathlength of a permeant gas. However, such a solution is generally notpreferred as it increases the container cost as more material and energyare consumed to make such a container. In addition, a thicker containerhas an adverse environmental footprint due to its increased weight,production energy, and transportation fuel consumption. While not apreferred option, this approach imposes an upper limit constraint on theadditional cost incurred to improve gas barrier performance.

The specialized nature of both active and passive gas barrier systemsmakes them significantly more expensive than the base PET resin. Betweenthe high cost of these special polymers, such as MXD6 and EVOH, and theoption of increasing PET container thickness, one commercial solution isto put these special barrier polymers into a multi-layer structuredcontainer such that a dedicated, but thin, layer(s) of the expensivebarrier polymer is used. In a three-layer container, the middle layermay be 1.5% to 15% of the average container thickness, and therefore asimilar minority percentage of the overall container weight, allowing ofcourse, for material density differences.

Nylon based special gas barrier resins have deficiencies, even when usedin relatively small amounts. They can delaminate during or after blowmolding due to insufficient adhesion between layers, cause undesirableyellow color and/or haze, and act as a contaminate in the existingpost-consumer PET recycling streams.

The recyclability issue with nylon based PET containers is important. Arelatively small amount of these additives, which may help prolongshelf-life for consumers by some weeks, can render the entire,predominantly-PET container unattractive for recycling.

Poly(glycolic acid), or PGA, polymer has been proposed as an attractivepassive gas barrier layer (typically, B-layer) for packagingapplications. PGA is attractive, in part or in whole, due to its smallmolecule repeating unit, high degree of polymer chain flexibility, tightmolecular packing, high degree of crystallinity, and high density, ascompared with PET. All of these features of PGA polymer can beassociated with lower gas permeability (e.g. better gas barrier) versusPET.

PGA is also attractive as a gas barrier in multi-layer containerstructures because of its relatively low impact on the PET recyclingprocess. PGA rapidly de-polymerizes and dissolves in aqueous causticsolutions typically employed for bottle and/or flake washing in PETrecycling operations. Therefore, PGA can be easily separated and removedfrom Recycled PET (RPET) process and product so that it does notcontaminate new production of containers utilizing RPET content.

Ease of PGA de-polymerization, while good for PET recycling, presents achallenge to producing sufficiently high molecular weight PGA withsufficiently high melt-viscosity, that can be melt-processed togetherwith PET to cost-effectively manufacture a high-quality, multi-layercontainer with enhanced gas barrier performance.

Several previous disclosures have described technical aspects relevantto the pursuit of stable, high-molecular weight PGA or poly(lacticacid), or PLA, or co-polymers of PGA and PLA. This includes:

U.S. Pat. No. 5,470,955 generally describes similarities between PLA andPGA polymers and methods of making PLA/PGA. Pre-polymerization isdirected towards forming end-capped polymers with terminal amide and/orother groups.

U.S. 2015/0291733 describes polyesters that include an aromatic orhetero-aromatic portion which distinguishes from aliphatic polyesterssuch as PGA. Di-functional monomers such as adipic acid can be used asco-monomers when the acid is subject to polymerization in the presenceof a metal-based catalyst.

U.S. Pat. No. 5,936,045 describes a process for making polyether esterscontaining at least 20% adipic acid monomer units. No pre-polymerformation is described.

U.S. Pat. No. 8,362,158 describes ring-opening polymerization of aglycolide (i.e. a glycolic acid cyclic dimer) with the use of ametal-based ring-opening catalyst. Adipic acid may be present as aco-monomer and oxazolines may be used as end-capping groups.

U.S. 2014/0148534 describes a process for making a polymer by reacting astarch with a low molecular weight PGA.

WO 2016/071574 describes prior work of some of the present inventors.Catalysts used for the formation of PGA from glycolic acid are sulfonicacid-based. The pre-polymer has a hydroxyl group termination of greaterthan 50%.

U.S. 2016/0060387 describes the use of a conventional metal-basedpolymerization catalyst to for a PGA pre-polymer with high hydroxylgroup termination.

U.S. Pat. No. 8,987,343 describes polymerization of a hydroxy-acid toform a three-dimensional network. Polymerization is carried out in thesolid-state.

U.S. Pat. No. 10,035,876 describes polymerization of a hydroxy-acid toform a three-dimensional network that gives rise to non-Newtonianviscoelastic behavior in the melt state.

U.S. 2006/0047088 describes a process in which PGA is made by catalyzedring-opening of a cyclic dimer.

U.S. 2014/0024769 describes the use of ring-opening catalysis to for PGAfrom glycolide that is derived from biomass. Pre-polymerization may becarried out with adipic acid. The pre-polymer may be chain lengthened byexposure to an oxazoline.

SUMMARY OF THE INVENTION

The present disclosure relates to reduction of gas molecule permeabilitythrough a polyethylene terephthalate (PET) polyester film or containerwall by introducing a discrete layer of a poly(hydroxy acid) (e.g.,poly(glycolic acid) or PGA) to inhibit the diffusion of gas moleculesinto and/or out of the food or beverage container. In one embodiment thepresent disclosure relates to a PGA composition that contains a stable,high molecular weight, high-viscosity PGA polymer that can beco-processed with PET into multi-layer structures (e.g. containers,films, etc.) having excellent gas barrier and recyclabilitycharacteristics. The poly(glycolic acid) of this invention has aparticular structure and its method of production is especiallyefficient and utilizes a small manufacturing footprint.

High molecular weight PGA can be produced by pre-polymerizing(polycondensing) glycolic acid (GA) followed by chain-extension toachieve a desired molecular weight.

Chain-terminating compounds that can inhibit polymerization are includedin the PGA polymer and rendered harmless in a preferred embodiment ofthis disclosure.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 describes the chemistry of forming a poly(hydroxy acid) polymer.

FIG. 2 shows time, temperature, and pressure changes in a process formaking an intermediate hydroxy-acid polymer.

FIG. 3 shows comparative examples of the capillary melt viscosity forlinear and branched PGA polymers.

FIG. 4 shows comparative examples of the capillary melt viscosity forbranched PGA polymers.

FIG. 5 shows examples of polymer stability from 3-30 minutes showing theimpact of BOX chain extender on apparent polymer melt viscosity.

FIG. 6 shows examples of polymer stability from 3-30 minutes showing theeffect of branched initiator and chain extender on apparent meltviscosity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the disclosure are shown.

As used herein, the words “a” and “an” and the like carry the meaning of“one or more”. Within the description of this disclosure, where anumerical limit or range is stated, the endpoints are included unlessstated otherwise. Also, all values and subranges within a numericallimit or range are specifically included as if explicitly written out.

As used herein, the words “about” or “substantially similar” may be usedwhen describing magnitude and/or position to indicate that the valueand/or position described is within a reasonable expected range ofvalues and/or positions. For example, a numeric value may have a valuethat is +/−0.1% of the stated value (or range of values), +/−1% of thestated value (or range of values), +/−2% of the stated value (or rangeof values), +/−5% of the stated value (or range of values), +/−10% ofthe stated value (or range of values), or +/−15% of the stated value (orrange of values).

The membrane, layer or methods disclosed herein can “comprise”, “consistessentially of”, or “consist of” particular components, compositions,method steps disclosed throughout the specification. A membrane or layerconsisting essentially of the components as defined herein does notexclude materials that do not materially affect the basic and novelcharacteristic(s) of the membrane or layer. For example, othercomponents may be included in the membrane or layer so long as the othercomponents do not substantially change the surface morphology, gasbarrier resistance, and/or stiffness.

As used herein, “composite” refers to a combination of two or moredistinct constituent materials into one. The individual components, onan atomic level, remain separate and distinct within the finishedstructure. The materials may have different physical or chemicalproperties, that when combined, produce a material with characteristicsdifferent from the original components.

The present disclosure includes a composite membrane or layer,containing, comprising, consisting essentially of, or consisting of apoly(hydroxy acid) polymer such as a poly(glycolic acid) polymer (PGA).

The composite membrane or layer disclosed herein may be a thin filmmembrane, a flat sheet membrane, a tubular membrane, and/or embodied asa sealable container. The composite membrane or layer may be in the formof various shapes, for example, flat (e.g., for a disc-shaped membrane),bent, curved (e.g., a cylinder shaped membrane), and rippled. In oneembodiment, a surface of the composite membrane is curved. In apreferred embodiment, the surface of the composite membrane is curvedand forms a bottle having an opening and cavity defined by the membraneor film. The composite membrane may have microscopic wrinkles, pores,bumps, ridges, etc. and still have a substantially “flat”macrostructure.

In one embodiment, the composite membrane or layer is a thin film havinga thickness of 20-2,000 μm, 25-1,500 μm, 50-1,000 μm, 100-800 μm,200-600 μm, 250-500 μm, or 300-400 μm. In a preferred embodiment, thecomposite membrane or layer is cylindrical and has a diameter of 10-100mm, 20-80 mm, 30-60 mm, 40-50 mm, or about 47 mm.

The present disclosure includes a multi-step process that uses acoupling agent for producing stable, high molecular weight, highviscosity poly(hydroxy acid) polymer (e.g., poly(glycolic acid) PGApolymer). Of particular interest are (1) the multi-step melt-solid-meltphase process which provides a stable intermediate polymer with highpercentage of carboxyl-terminated chain ends and a final polymer withsuitably high molecular weight, and (2) the capability to renderharmless any deleterious chain-terminating compounds typically found inless purified (technical) grades of glycolic acid (GA), as compared tomore pure cosmetic-grade glycolic acid.

The process described in the present disclosure forms a poly(hydroxyacid) polymer such as a poly(glycolic acid) polymer, or a copolymerthereof, by one or more polycondensation reactions. The polycondensingis preferably carried out in the presence of an acid catalyst toincrease molecular weight and/or to form telechelic polymers having highthermally stability. A step-growth polycondensing (e.g., solid statepolycondensation) process provides a final poly(hydroxy acid) polymer ofhigh molecular weight and high thermal stability. FIG. 1 provides asimplified description of the chemical reactions of a process forforming a poly(hydroxyl acid) polymer.

In another preferred embodiment of the invention, chain-terminatingcompounds which exist in certain commercial grades of glycolic acid rawmaterials intended for non-cosmetic end-uses, may be rendered harmlessby addition of multi-functional reaction initiator(s) at the onset ofliquid/melt-phase polycondensation. In the context of the presentdisclosure harmless conveys that an impurity-containing hydroxyl acid(e.g., glycolic acid) feedstock may be used for forming a poly(hydroxyacid) polymer (e.g., PGA) that provides the same or similar chemical andphysical properties in comparison to a corresponding polymer made with afeedstock that is free of the impurities or contains such impurities insubstantially lesser amounts such as 30% fewer impurities, preferably40%, 50%, 60%, 70% 80% or 90% fewer purities.

The multi-functional initiator gives rise to multi-branched polymerchains which continue to polymerize, either during polycondensation orreactive extrusion chain extension, or both, even when achain-terminator (e.g., an impurity that acts to terminatepolymerization or polymer chain extension) reacts into one or morebranches of the polymer chain. Additionally, the presence of themulti-functional reaction initiator in conjunction with a di-functionalreaction initiator may also effectively diminish chain terminatedpolymer formation (e.g., a linear polymer especially short linearpolymer chains) and the consumption of hydroxy acid monomers caused bythese chain terminators which are present in the feedstock monomers ofembodiments the present disclosure. Of the chain terminators, acidcompounds in general and specifically methoxyacetic acid (MAA) may bepresent. MAA, because it has only one reactive end group, can inhibitpolymerization of linear poly(glycolic acid). Once MAA is incorporatedinto a linear, diol- or di-acid-initiated polymer chain it inhibitspolymer growth by terminating chain growth at the polymer end to whichit has reacted. Similarly, chain-terminating hydroxyl compounds caninhibit polycondensation and chain extension of linear, di-acid- ordiol-initiated poly(hydroxy acid) polymer. Chain-terminating compoundsmay be present in an amount of 0.01 to 5% by weight based on the weightof the glycolic acid (or other hydroxy acid such as lactic acid) rawmaterial, preferably 0.02 to 2% by weight, more preferably 0.05 to 1% byweight, and most preferably 0.1 to 0.5% by weight.

Statistically, as greater amounts of a multi-functional initiator areadded to the starting recipe (e.g., a reaction mixture that comprises ahydroxy acid monomer and associated impurities, catalyst and/orinitiator), the less impact the chain-terminating compounds will have on(1) reaction rate, (2) completion of polymerization, and (3) ultimatemolecular weight of the poly(hydroxy acid) polymer. However, increasingthe total concentration of reaction initiators, whether di- ormulti-functional, will necessarily result in lower intermediate polymermolecular weight and/or less extendable polymer chains.

Thus, there exists a preferred balance among the (A) di-functionalinitiator, (B) multi-functional initiator, and (C) chain-terminatingcompounds which results in the most desirable high molecular weightintermediate polymer and structure of the final poly(hydroxy acid)polymer and which also permits acceptable reaction kinetics toefficiently form a polymer product

In order for the final polymer to have a suitable balance of properties(A) should have a weight percentage of less than 3.0% of the finalpolymer, (B) should have a weight percentage of less than 1.2% of thefinal polymer, and (C) should have a weight percentage of less than 1%of the final polymer. Preferably, (A) has a weight percentage between0.5 and 2.5% of the final polymer, (B) has a weight percentage between0.2 and 1.0% of the final polymer, and (C) has a weight percentagebetween 0.1 and 1.0% of the final polymer. More preferably, (A) has aweight percentage between 0.75 and 2.0% of the final polymer, (B) has aweight percentage between 0.3 and 0.8% of the final polymer, and (C) hasa weight percentage between 0.1 and 0.7% of the final polymer. And mostpreferably, (A) has a weight percentage between 1.0 and 1.5% of thefinal polymer, (B) has a weight percentage between 0.4 and 0.6% of thefinal polymer, and (C) has a weight percentage between 0.15 and 0.45% ofthe final polymer.

From the preferred combination of ingredients we see that final polymerproperties may be influenced by the combination of linear and branchedpolymer chains which are typically present in the intermediate polymer.In one embodiment the linear polymer chains are comprised ofmono-functional and di-functional polymer chains, where amono-functional chain may be initiated from ingredient (C) and adi-functional chain may be initiated from ingredient (A). Themono-functional polymer chain may be formed by chain extensions fromonly a single end (e.g., polymerization site) whereas the di-functionalpolymer chain may be formed by chain extensions from two ends (e.g., twopolymerization sites). Poly-functional or branched polymer chains may beformed by chain extension directly from ingredient (B).

By number, the ratio of linear chains to branched chains in theintermediate polymer is preferably 7-3:1, preferably 6-4:1 or about5-4.5:1. More preferably, the number ratio of linear to branchedintermediate polymer chains should be between 4 to 1 and 6 to 1. Andmost preferably, the number ratio of linear to branched chains should beabout 4.5 to 1 in the intermediate polymer.

During reactive extrusion linear chains may combine with other linearchains to form larger but fewer linear chains. Linear chains may alsocombine with branched chains to eliminate linear chains in favor oflarger branched chains. Following reactive extrusion and the combinationof linear and branched intermediate polymer chains into the finalpolymer, the number ratio of linear to branched chains decreases.Preferably, the number ratio of linear to branched chains in the finalpolymer is less than 4:1, more preferably less than 3:1, and mostpreferably between about 2:1 to about 1:1. However, if the number ratioof linear to branched chains in the final polymer is too small, forexample less than 1:1, the physical properties of the final polymer maybecome unsuitable for downstream melt processing. For example, excessivebranching may directly cause the final polymer melt viscosity to be toohigh for injection molding of multi-layer containers. Alternatively,excessive final polymer branching may lead to polymer propertyinstability due to thermal degradation, cross-linking or other relatedphenomena.

The majority of the hydroxy acid monomer is preferably glycolic acid,L-lactic acid and/or D-lactic acid. Particularly interestingcompositions of the poly(hydroxy acid) polymer and copolymer include, inaddition to glycolic acid:

-   -   one or more organic linear, branched, cyclic, aromatic or        polymeric monomers containing two or more hydroxy, carboxylic        acid, or thiol groups, and/or    -   a hydroxy acid co-monomer, or its equivalent lactone, of general        formula:        HO(CH₂)_(n)CHR(CH₂)_(m)COOH    -   wherein    -   R is independently selected from a group consisting of hydrogen,        linear alkyl, alkenyl alkynyl, branched alkyl, cyclic alkyl and        aryl moieties, and    -   n and m are integers which can independently vary between 0 and        20.

In a particularly preferred embodiment, the molar ratio between residuesderived from glycolic acid (or hydroxy acid) and residues derived from aco-monomer is 1000:1 or less, for example 500:1 or less, suitably 300:1or less, advantageously 45:1 to 55:1, in particular 48:1 to 52:1.

In one embodiment, the polycondensation (e.g., the formation of apoly(hydroxy acid) polymer by reaction of hydroxy acid monomer in thepresence of an initiator and/or catalyst) is initiated with a diol or adi-acid. For dial initiation the initiators (which can also serve asco-monomers) are preferably selected from hydroxy-terminated compounds(diols, triols, tetraols, pentaols), such as propanediol, butanediol,hexanediol, pentaerythriol and oligomeric polyethylene glycol andcombinations thereof, to produce a hydroxy-terminated telechelicpolymer. Other diols or di-acids may include an aliphatic polyvalentcarboxylic acid, an aliphatic polyhydric alcohol, aliphatichydroxycarboxylic acid, and aliphatic lactone, specifically, aliphaticpolyvalent carboxylic acids such as succinic acid, adipic acid, sebacicacid, and fumaric acid, or derivatives thereof, aliphatic polyhydricalcohols such as ethylene glycol, propylene glycol, butanediol,hexanediol, octanediol, neopentyl glycol, glycerin, isosorbide,trimethylolpropane, pentaerythritol, an aliphatic polyvalent alcohol inwhich ethylene oxide or propylene oxide is added to trimethylolpropaneor pentaerythritol, diethylene glycol, triethylene glycol, polyethyleneglycol, and polypropylene glycol, or derivatives thereof, aliphatichydroxycarboxylic acids such as lactic acid, citric acid, malic acid,glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid,4-hydroxyvaleric acid, and 6-hydroxycaproic acid, and aliphatic lactonessuch as glycolide, ε-caprolactone, ε-caprolactone, β-propiolactone,δ-butyrolactone, δ- or γ-butyrolactone, pivalolactone, and6-valerolactone. A mixture of component units may be used. Themultifunctional initiator preferably includes trimellitic acid,glycerol, pentaerytritol, and/or trimethylol.

The thermal stability of the final polymers and copolymers thus producedare good, typically exhibiting a glass transition point in excess of 35°C., preferably in excess of 37° C. and even up to 50° C., anddecomposition temperatures, T_(d 10%) of at least 280° C., in particularat least 295° C.

The polycondensation is preferably carried out in the presence of acatalyst which is preferably an inorganic compound, such as antimony,tin, or cobalt. In addition, a sulphonic acid-containing organiccompound may be used, preferably in combination with the inorganiccompound. The amount of the inorganic and/or organic compound(s) ispreferably from 0.001 to 0.5% by weight of the glycolic acid togetherwith the co-monomers, more preferably 0.002 to 0.2% by weight, even morepreferably 0.005 to 0.1% by weight, and most preferably 0.01 to 0.05% byweight.

The sulfonic acid group-containing organic compound preferably has aboiling point of 200° C. or higher or a melting point of 160° C. orhigher at atmospheric pressure. Further preferable is a sulfonic acidgroup-containing organic compound having a melting point of 180° C. orhigher. Examples include aromatic sulfonic acids such asn-butylbenzenesulfonic acid, n-octylbenzenesulfonic acid,n-dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid,2,5-dimethylbenzenesulfonic acid, 2,5-dibutylbenzenesulfonic acid,o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid,p-aminobenzenesulfonic acid, 3-amino-4-hydroxybenzenesulfonic acid,5-amino-2-methylbenzenesulfonic acid,3,5-diamino-2,4,6-trimethylbenzenesulfonic acid,2,4-dinitrobenzenesulfonic acid, 2,5-dichlorobenzenesulfonic acid,p-phenolsulfonic acid, cumenesulfonic acid, xylenesulfonic acid,o-cresolsulfonic acid, m-cresolsulfonic acid, p-cresolsulfonic acid,2-naphthalenesulfonic acid, 1-naphthalenesulfonic acid,isopropylnaphthalenesulfonic acid, dodecylnaphthalenesulfonic acid,dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid,1,5-naphthalenedisulfonic acid, 1,6-naphthalenedisulfonic acid,2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid,1,3,6-naphthalenetrisulfonic acid, 4,4-biphenyldisulfonic acid,anthraquinone-2-sulfonic acid, o-benzenedisulfonic acid,m-benzenedisulfonic acid, p-benzenedisulfonic acid,2,5-diamino-1,3-benzenedisulfonic acid phenol-2,4-disulfonic acid,aniline-2,4-disulfonic acid, anthraquinone-1,5-disulfonic acid,benzidinedisulfonic acid, 1-naphthol-2-sulfonic acid,2-naphthol-3,6-disulfonic acid, 2-naphthol-6,8-disulfonic acid,1,3,5-benzenetrisulfonic acid, and polystyrenesulfonic acid, andaliphatic sulfonic acids and alicyclic sulfonic acids such asn-octylsulfonic acid, pentadecylsulfonic acid, 1,2-ethanedisulfonicacid, 1,3-propanedisulfonic acid, methanedisulfonic acid,1,4-butane-disulfonic acid, pentanedisulfonic acid, hexanedisulfonicacid, heptanedisulfonic acid, octane-disulfonic acid, nonanedisulfonicacid, decanedisulfonic acid, 1,11-undecanedisulfonic acid.1,12-dodecanedisulfonic acid, catechol-3,5-disulfonic acid,cyclopentanesulfonic acid, cyclohexanesulfonic acid and camphorsulfonicacid, taurine, dinonylnaphthalenedisulfonic acid,1,5-naphthalenedisulfonic acid, 1,6-naphthalenedisulfonic acid,2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid,1,3,6-naphthalenetrisulfonic acid, 4,4-biphenyldisulfonic acid,o-benzenedisulfonic acid, in-benzenedisulfonic acid, p-benzenedisulfonicacid, 2,5-diamino-1,3-benzenedisulfonic acid, phenol-2,4-disulfonicacid, aniline-2,4-disulfonic acid, anthraquinone-1,5-disulfonic acid,benzidinedisulfonic acid, 2-naphthol-3,6-disulfonic acid,2-naphthol-6,8-disulfonic acid, 1,3,5-benzenetrisulfonic acid, andpolystyrenesulfonic acid.

Inorganic catalysts such as metal catalysts include metal compounds suchas tin compounds, titanium compounds, lead compounds, zinc compounds,cobalt compounds, iron compounds, lithium compounds, and rare earthcompounds and, as a kind of the compounds, metal alkoxide, metal halide,organic carboxylate, carbonate, sulfate, and oxide are preferable.Specifically, examples include tin compounds such as a tin powder, tin(II) chloride, tin (IV) chloride, tin (II) bromide, tin (IV) bromide,ethoxytin (II), t-butoxytin (IV), isopropoxytin (IV), tin (II) acetate,tin (IV) acetate, tin (II) octylate, tin (II) laurate, tin (II)myristate, tin (II) palmitate, tin (II) stearate, tin (II) oleate, tin(II) linolate, acetylacetone tin (TI), tin (II) oxalate, tin (TT)lactate, tin (IT) tartarat, tin (TI) pyrophosphate, tin (TI)p-phenolsulfonate, tin (II) bis(methanesulfonate), tin (II) sulfate, tin(II) oxide, tin (IV) oxide, tin (II) sulfide, tin (IV) sulfide,dimethyltin (IV) oxide, methylphenyltin (IV) oxide, dibutyltin (IV)oxide, dioctyltin (IV) oxide, diphenyltin (IV) oxide, tributyltin oxide,triethyltin (IV) hydroxide, triphenyltin (IV) hydroxide, tributyltinhydride, monobutyltin (IV) oxide, tetramethyltin (IV), tetraethyltin(IV), tetrabutyltin (IV), dibutyldiphenyltin (IV), tetraphenyltin (IV),tributyltin (IV) acetate, triisobutyltin (IV) acetate, triphenyltin (IV)acetate, dibutyltin diacetate, dibutyltin dioctanoate, dibutyltin (IV)dilaurate, dibutyltin (IV) maleate, dibutyltin bis(acetylacetonate),tributyltin (IV) chloride, dibutyltin dichloride, monobutyltintrichloride, dioctyltin dichloride, triphenyltin (IV) chloride,tributyltin sulfide, tributyltin sulphate, tin (II)trifluoromethanesulfonate, ammonium hexachlorostannate, dibutyltinsulfide, diphenyltin sulfide, triethyltin sulfate and phthalocyanine tin(II) and, among them, tin compounds other than tin (II) chloride arepreferable.

Titanium compounds such as titanium methoxide, titanium propoxide,titanium isopropoxide, titanium butoxide, titanium isobutoxide, titaniumcyclohexide, titanium phenoxide, titanium chloride, titanium diacetate,titanium triacetate, titanium tetraacetate, and titanium (IV) oxide.Lead compounds include diisopropoxylead (II), lead monochloride, leadacetate, lead (II) octylate, lead (II) isooctanoate, lead (II)isononanate, lead (II) laurate, lead (II) oleate, lead (II) linolate,lead naphthenate, lead (II) neodecanoate, lead oxide, and lead (II)sulfate, zinc compounds include zinc powder, methylpropoxyzinc, zincchloride, zinc acetate, zinc (II) octylate, zinc naphthenate, zinccarbonate, zinc oxide, and zinc sulfate, cobalt compounds include cobaltchloride, cobalt acetate, cobalt (II) octylate, cobalt (II)isooctanoate, cobalt (II) isononanate, cobalt (II) laurate, cobalt (II)oleate, cobalt (II) linolate, cobalt naphthenate, cobalt (II)neodecanoate, cobalt (II) carbonate, cobalt (II) sulfate, and cobalt(II) oxide, iron compounds include iron (II) chloride, iron (II)acetate, iron (II) octylate, iron naphthenate, iron (II) carbonate, iron(II) sulfate, and iron (II) oxide, lithium compounds such aspropoxylithium, lithium chloride, lithium acetate, lithium octylate,lithium naphthenate, lithium carbonate, dilithium sulfate, and lithiumoxide, and rare earth compounds such as triisopropoxyeuropium (III),triisopropoxyneodymium (III), triisopropoxylanthanum,triisopropoxy-samarium (III), triisopropoxyyttrium, isopropoxyyttrium,dysprosium chloride, europium chloride, lanthanum chloride, neodymiumchloride, samarium chloride, yttrium chloride, dysprosium (III)triacetate, europium (III) triacetate, lanthanum acetate, neodymiumtriacetate, samarium acetate, yttrium triacetate, dysprosium (III)carbonate, dysprosiunl (IV) carbonate, europium (II) carbonate,lanthanum carbonate, neodymium carbonate, samarium (II) carbonate,samarium (III) carbonate, yttrium carbonate, dysprosium sulfate,europium (II) sulfate, lanthanum sulfate, neodymium sulfate, samariumsulfate, yttrium sulfate, europium dioxide, lanthanum oxide, neodymiumoxide, samarium (III) oxide, and yttrium oxide.

Other metal compounds include potassium isopropoxide, potassiumchloride, potassium acetate, potassium octylate, potassium naphthenate,tert-butyl potassium carbonate, potassium sulfate, and potassium oxide,copper compounds such as copper (II) diisopropoxide, copper (II)chloride, copper (II) acetate, copper octylate, copper naphthenate,copper (II) sulfate, and dicopper carbonate. nickel compounds such asnickel chloride, nickel acetate, nickel octylate, nickel carbonate,nickel (II) sulfate, and nickel oxide, zirconium compounds such astetraisopropoxyzirconium (IV), zirconium trichloride, zirconium acetate,zirconium octylate, zirconium naphthenate, zirconium (II) carbonate,zirconium (IV) carbonate, zirconium sulfate, and zirconium (II) oxide,antimony compounds such as triisopropoxy-antimony, antimony (III)fluoride, antimony (V) fluoride, antimony acetate, and antimony (III)oxide, magnesium compounds such as magnesium diisopropoxide, magnesiumchloride, magnesium acetate, magnesium lactate, magnesium carbonate,magnesium sulfate, and magnesium oxide, calcium compounds such asdiisopropoxycalcium, calciunl chloride, calcium acetate, calciumoctylate, calcium naphthenate, calcium lactate, and calcium sulfate,aluminum compounds such as aluminum, aluminum isopropoxide, aluminumchloride, aluminum acetate, aluminum octylate, aluminum sulfate, andaluminum oxide, gennanium compounds such as germanium,tetraisopropoxygermane, and germanium (IV) oxide, manganese compoundssuch as triisopropoxymanganese (III), manganese trichloride, manganeseacetate, manganese (II) octylate, manganese (II) naphthenate, andmanganese (II) sulfate, bismuth compounds such as bismuth (III)chloride, bismuth powder, bismuth (III) oxide, bismuth acetate, bismuthoctylate, and bismuth neodecanoate.

An acid catalyst other than the sulfonic acid group-containing compoundmay be a Bronsted acid which is a proton donor, or a Lewis acid which isan electron pair acceptor, and may be either an organic acid or aninorganic acid. Examples include monocarboxylic acid compounds such asformic acid, acetic acid, propionic acid, heptanoic acid, octanoic acid,octylic acid, nonanoic acid, isononanoic acid, trifluoroacetic acid andtrichloroacetic acid, dicarboxylic acid compounds such as oxylic acid,succinic acid, maleic acid, tartaric acid and malonic acid,tricarboxylic acid compounds such as citric acid and tricarballylicacid, acidic amino acids such as aspartic acid and glutamic acid,ascorbic acid, retinoic acid, phosphoric acid, metaphosphoric acid,phosphorous acid, hypophosphorous acid, polyphosphoric acid, phosphoricacid monoester such as monododecyl phosphate and monooctadecylphosphate, phosphoric acid diester such as didodecyl phosphate anddioctadecyl phosphate, phosphoric acid compounds such as phosphorousacid monoester and phosphorous acid diester, boric acid, hydrochloricacid, and sulfuric acid. In addition, the acid catalyst other than thesulfonic acid group-containing compound is not particularly limited in ashape, and may be any of a solid acid catalyst and a liquid acidcatalyst, and examples of the solid acid catalyst include naturalminerals such as acid clay, kaolinite, bentonite, montmorillonite, talc,zirconium silicate and zeolite, oxides such as silica, alumina, titaniaand zirconia, or oxide complexes such as silica alumina, silicamagnesia, silica boria, alumina boria, silica titania and silicazirconia, chlorinated alumina, fluorinated alumina, and cation exchangeresin.

The process includes a liquid/melt-phase polymerization, followed by asolid-state polymerization, followed by a melt-phase chain-extension inan extruder. PGA is relatively sensitive to high temperatures. However,production of PGA with the desired structure (high molecular weight andend-group composition) requires long polymerization times at elevatedtemperatures. In one embodiment the process includes apre-polymerization step in which a hydroxy acid monomer is subject totwo steps: (1) condensation polymerization of glycolic acid in theliquid/melt phase at temperatures of 190-220° C. followed by (2)solid-state polymerization (SSP) at temperatures of 140-185° C. which isbelow the melt-point of the polymer but high enough for thepolycondensation reaction to proceed. Conventionally, the transitionbetween liquid/melt and solid phase steps was accomplished via arelatively complicated procedure including emptying the reactor afterpre-polymerization, then solidifying, crushing, grinding, and sievingthe pre-polymer followed by SSP in a separate second reactor.

In a preferred embodiment of the present disclosure, both liquid/meltcondensation polymerization and SSP are conducted in a single reactorincluding solidifying between the two reaction stages without emptying,crushing, grinding or sieving outside the reactor between the tworeaction stages. A Lodige-type vacuum paddle dryer equipped with strongmixer blades, high-speed homogenizer mixer, and heating/cooling jacketis preferred for this process. All ingredients are introduced into thereactor at ambient temperature and pressure. The reactor is then sealedand under constant agitation the temperature in increased so as to boiloff the excess water typically included with the hydroxy-acid. Once thewater has been removed, the reactor temperature is raised to thereaction temperature (nominally 200° C.). The ingredients undergomelt-phase reaction for 1-5 hours to form a poly(hydroxy acid)pre-polymer. Following conclusion of the melt-phase, solidification ofpoly(hydroxy acid) pre-polymer is done by rapidly lowering the reactorjacket temperature. During precipitation and solidification, PGApre-polymer (e.g., precursor to the intermediate polymer) spontaneouslycrystallizes. Pre-polymer solidified after liquid/melt polycondensationis sufficiently brittle for the homogenizer mixer to grind thesolidifying material in-situ and form sufficiently fine particles forthe SSP reaction to proceed with satisfactory speed. The SSP reactionmay be carried out for 24-96 hours at temperatures between 140-180° C.After SSP, the solid-stated pre-polymer (referred to as intermediatepolymer) can be removed from the reactor as a solid powder with particlesize suitable for chain extension to be performed in a melt extruder.Notably, these preferred embodiments save investment and operationscosts.

After removal from the Lodige type reactor, an intermediate polymer withweight-average molecular weight (M_(w)) as measured by Size Exclusion(Gel Permeation) Chromatography (GPC) between 15,000 and 40,000 must bedried to less than 50 ppm moisture prior to chain-extension via reactiveextrusion. Preferably the drying is carried out in situ in the samevacuum reactor in which the melt-phase and solid-phase polycondensingwas carried out. The resulting material is then subject to chainextension by reaction in a mixing extruder to form the final polymer.

Chain-extension is carried out in any type of melt-extruder withsufficient mixing, temperature and residence time to e t mix, and reactthe intermediate polymer with a preferred bis-oxazoline-basedchain-extender. Since the ingredients are fed into the extruder as solidpowders, the extruder temperature starts low (20-60° C.) and increasesto 220-260° C. whereupon the chain-extension reaction proceeds rapidly.Reactive extrusion residence time is typically 30 to 150 seconds,depending on the temperature and required degree of chain-extension.After reactive extrusion chain-extension and pelletization, either byunderwater die-face cut or strand cut pelletization, the M_(w) of theresultant PGA polymer as measured by Size Exclusion (Gel Permeation)Chromatography (GPC) is between 100,000 and 200,000, more preferablybetween 120,000 and 180,000, or more preferably between 140,000 and160,000.

An oxazoline chain extender (e.g., a di-functional BOX reactive couplingagent and/or a multi-functional BOX reactive coupling agent) is amolecule having one or more oxazoline groups. The term “BOX” generallyrefers to a bis-oxazoline compound having at least two oxazoline groups.The oxazoline group may be substituted at one or more carbon atoms witha substituent or linker unit that binds a further oxazoline group tothereby for a BOX compound. The oxazoline group is shown below.

Examples of oxazolines include compounds such as2,2′-m-phenylene-bis(2-oxazoline), 2,2′-p-phenylene-bis (2-oxazoline),2-phenyl-2-oxagoline, and styrene-isopropenyl-2-oxazoline; oxazinecompounds, such as 2-methoxy-5, 6-dihydro-4H-I, 3-oxazine; and oxazolinecompounds having a chiral center such as2,2′-bis[(4S)-4-benzyl-2-oxazoline],2,2-bis((4S)-(−)-4-isopropyloxazoline)propane,(4S)-(+)-4-[4-(tert-butyl)phenyl]-α-[(4S)-4-[4-(tert-butyl)phenyl]-2-oxazolidinylidene]-2-oxazolineacetonitrile,(+)-2,2′-isopropylidenebis[(4R)-4-benzyl-2-oxazoline],2,2′-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline],(−)-2,2′-isopropylidenebis[(4S)-4-phenyl-2-oxazoline],(+)-2,2′-isopropylidenebis[(4R)-4-phenyl-2-oxazoline],2,2′-methylenebis[(4S)-4-tert-butyl-2-oxazoline],[3aR-[2(3′aR*,8′aS*),3′aβ,8′aβ]]-(+)-2,2′-methylenebis[3a,8a-dihydro-8H-indeno[1,2-d]oxazole],(3aS,3′aS,8aR,8′aR)-2,2′-methylenebis[3a,8a-dihydro-8H-indeno[1,2-d]oxazole],2,2′-methylenebis[(4R,5S)-4,5-diphenyl-2-oxazoline],2,2′-methylenebis[(4S)-4-phenyl-2-oxazoline],(4S,4'S)-(−)-2,2′-(3-pentylidene)bis(4-isopropyloxazoline),(4S)-(+)-phenyl-α-[(4S)-phenyloxazolidin-2-ylidene]-2-oxazoline-2-acetonitrile.

In a preferred embodiment of the process, the polycondensing,crystallizing and solid-state polycondensing are carried out in a vacuumreactor to form the intermediate polymer. The vacuum reactor is capableof achieving and maintaining a pressure lower than an ambient pressureoutside of the vacuum reactor. Preferably the vacuum reactor is able tocarry out the steps of polycondensing, crystallizing and/or solid-statepolycondensing at a pressure of 100-1,500 mbar, preferably 200-1,200,preferably 400-1,000, or 600-800 mbar. The pressure during any of thepolycondensing, crystallizing or solid-state polycondensing steps mayvary over time. Especially during the polycondensing of the liquidreaction mixture, the process may begin at ambient pressure and isgradually reduced to remove dissolved gases and atmosphere in the vacuumreactor. Preferably, after polycondensation of the liquid reactionmixture, vacuum is maintained to remove volatile byproducts of thereaction such as water, alcohol or low molecular weight volatile organicmaterials. The vacuum reactor s preferably maintained at a pressurelower than ambient pressure during the crystallizing and solid-statepolycondensing, preferably there is no break in vacuum during beginningat the crystallizing and extending through the solid-statepolycondensing thereby ensuring the dryness of the prepolymer material.

FIG. 2 describes the progression of pressure and temperature during aprocess of polycondensing, crystallizing and solid-state polycondensingPGA. At the initiation of the process the pressure inside the vacuumreactor is the same as ambient pressure. Pressure is gradually reducedas the temperature is increased. An increase in temperature in thepresence of a catalyst such as a sulfonic acid material leads to theformation of a poly(hydroxy acid) prepolymer and the release of water.As the pressure is further lowered and the temperature increases, waterand other byproducts formed during the polycondensing are removed fromthe vacuum reactor (e.g., the agitated polycondensation reactor). Thepolycondensing is continued until a desired temperature range (forexample 160-210° C.) is attained and at which time the pressure isoptionally reduced and maintained at a value of, for example, 200 mbaror less. The M_(w) of the thus formed polycondensed material ispreferably ≥10,000 by GPC, more preferably ≥12,000, ≥15,000, ≥18,000, or≥20,000.

Crystallizing occurs by rapidly dropping the temperature of the vacuumreactor (which preferably is jacketed thereby permitting cooling with aheat transfer medium) and the polycondensed liquid reaction mixturetherein. For example, the cooling rate may be 5° C./min. or greater,preferably 10° C./min. or greater, more preferably 20° C./min. orgreater. Preferably the temperature is reduced from 190-220° C. thenmaintained at a temperature of 140° C. or greater for the remainder ofthe crystallizing and, preferably, for the solid-state polymerizing. Arapid decrease in temperature promotes quick solidification andcrystallization of the polycondensed liquid reaction mixture. This inturn leads to fracturing and pulverization inside the agitated vacuumreactor.

The vacuum reactor is preferably a vacuum reactor that carries outagitation and de-volatilization of the reaction mixture in a singleapparatus/chamber. The vacuum reactor apparatus preferably has apaddle-type configuration to promote mixing of the viscous polycondensedmaterial and to impart sufficient force to the crystallized reactionmixture to permit its fracturing and pulverization to form a particulatematerial. Preferably agitation is continued throughout thepolycondensing and crystallizing phases of the process. Pressure ismaintained at a level sufficient to remove water and/or volatile organicmaterials formed during the polycondensing. The resultant crystallizedreaction material preferably has a water content of less than 100 ppm,more preferably less than 75 ppm, 50 ppm or most preferably less than 25ppm by weight based on the weight of the crystallized and pulverizedmaterial.

The vacuum reactor is preferably a cylindrical reactor arrangedhorizontally. A high speed homogenizer may be used together with thevacuum reactor to promote sufficient mixing of the pre-polymer materialformed by the polycondensing and to form a particulate material havingan average particle size that is preferably less than 10 mm, morepreferably less than 5 mm, more preferably less than 3 mm. Preferablymore than 90% by weight, more preferably 95% by weight or mostpreferably 98% by weight of the particulate crystallized material has aparticle size of less than 10 mm, preferably less than 5 mm morepreferably less than 3 mm.

The solid-state polycondensing of the crystallized and pulverizedmaterial is preferably carried out at a temperature of at least 140° C.and lower than the glass transition temperature of the poly(hydroxyacid) polymer to form the intermediate polymer. The solid statepolycondensing is preferably carried out at a temperature of from145-185° C., more preferably 155-175° C., and most preferably 160-170°C. The solid-state polycondensing is preferably carried out for hours,for example, from 2 to 96 hours, preferably 4-80 hours, more preferably8-72 hours, or most preferably 12-60 hours. Preferably the solid-statepolycondensing is carried out at a pressure of 400 mbar or less, morepreferably 290 mbar or less, or most preferably 100 mbar or less. Theresultant solid-state polycondensed material preferably has a weightaverage molecular weight of ≥20,000, preferably ≥25,000, more preferably≥30,000, or most preferably ≥35,000 The amount of hydroxyl- andcarboxyl-end group determination is preferably greater than 90% by mole,more preferably greater than 95% by mole, or most preferably greaterthan 98% by mole.

The solid-state polycondensed material is subsequently transferred to amelting and mixing reactor for combining with a BOX coupling agent andoptional additives. The coupling agent serves to further condense/react,through the end groups, the solid reaction mixture formed by thesolid-state polycondensing. This leads to an overall increase in themolecular weight and forms the final polymer. Combining the couplingagent and the solid material obtained from the solid-statepolycondensing may be carried out concurrently or separately from thestep of melting the solid-state polycondensed material. Most preferably,the solid-state polycondensed material is fed into a mixing extrudertogether with the BOX coupling agent. Alternately, the BOX couplingagent may be added as a separate feed into an extruder port downstreamof the feed port such that the solid-state polycondensed material ismolten in the reaction extruder prior to exposure to the coupling agent.

In another preferred embodiment of the invention a process for making ahigh molecular weight poly(hydroxy acid) polymer comprising at least 90%by weight of reacted units of one or more hydroxy acid monomers andhaving a weight average molecular weight of >100,000 by GPC, comprises(1) mixing one or more hydroxy acid monomers selected from the groupconsisting of glycolic acid and lactic acid, at least one of a diolinitiator and a di-acid initiator, and at least one multifunctionalinitiator to form a liquid monomer mixture in an agitatedpolycondensation reactor, (2) polycondensing the liquid monomer mixtureto form a liquid reaction mixture comprising a pre-polymer having aweight average molecular weight of >10,000 by GPC, and greater than 80%by mole carboxyl or hydroxyl end-group termination, (desired end-grouptermination for a given recipe is either carboxyl or hydroxyl, but notboth for the same pre-/intermediate-polymer), (3) crystallizing theliquid reaction mixture in the agitated polycondensation reactor to forma first solid reaction mixture, (4) solid state polycondensing the solidreaction mixture to form a second solid reaction mixture having amoisture level less than 50 ppm by weight and comprising anintermediate-polymer having weight average molecular weight of >20,000by GPC, and greater than 90% by mole hydroxyl or carboxyl end-grouptermination, (desired end-group termination for a given recipe is eithercarboxyl or hydroxyl, but not both for the samepre-/intermediate-polymer), (5) mixing the second solid reaction mixturewith at least one of a di-functional BOX reactive coupling agent and amulti-functional BOX reactive coupling agent to form a coupling reactionmixture, and coupling the coupling reaction mixture in a melting andmixing extruder to form the final poly(hydroxy acid) polymer. Inaddition, it is preferable that the liquid monomer mixture remains inthe agitated polycondensation reactor during polycondensing, the liquidreaction mixture remains in the agitated polycondensation reactionduring crystallizing, and the second solid reaction mixture remains inthe agitated polycondensation reaction during the solid statepolycondensing such that the pre-polymer, and the first solid reactionmixture and the intermediate-polymer are not removed from the agitatedpolycondensation reactor prior to performing the coupling reaction. Itis also preferred that (1) the liquid reaction mixture is agitated inthe agitated polycondensation reaction during the crystallizing to formparticles of the solid reaction mixture, that (2) the average particlesize of the particles of the solid reaction mixture is less than 3 mm,that (3) crystallizing includes cooling the liquid reaction mixture to atemperature of no greater than 185° C. (the cooling temperature istypically the temperature that is planned for solid-state condensation),that (4) the liquid monomer mixture is reacted at a temperature ofgreater than or equal to ≥90° C. to 220° C., that (5) the solid reactionmixture is solid state polycondensed at a temperature of from 140° C. to≤185° C., that (6) the coupling reaction mixture is formed and coupledin the melting and mixing extruder, that (7) the liquid monomer mixtureis polycondensed at a temperature of 190-220° C. and the solid reactionmixture is solid state polycondensed at a temperature of 150-180° C.,that (8) crystallization includes cooling the liquid reaction mixture inthe agitated polycondensation reactor at a rate of 10° C./min orgreater, that (9) the solid pre-polymer temperature remains above 150°C. during the crystallizing and the solid state polycondensing, that(10) the pressure in the agitated polycondensation reactor remains below500 mbar during the polycondensing and the crystallizing.

The poly(hydroxy acid) (e.g., PGA) may be used to make one or morelayers of a container or film having improved gas barrier properties,preferably a container made with polyethylene terephthalate as a majorresin or co-major resin. Nevertheless, the poly(hydroxy acid) polymermay be used with many other thermoplastics of the polyester type.Examples of such other materials include polyethylene 2.6- and1,5-naphthalate (PEN), PETG, poly(tetramethylene 1,2-dioxybenzoate) andcopolymers of ethylene terephthalate and ethylene isophthalate.

The poly(hydroxy acid) polymer may also be used with one or morerecycled resins and/or may be recycled as mixture with a PET resin.“Recycled” refers to a broad category of materials that have beenreprocessed. “Post-Consumer Recycled” (or PCR) refers to materials whichhave been recovered after commercial use. Recycled materials includepost-consumer recycled materials in addition to materials that have beenrecovered at any other point during processing or use.

In an especially preferred embodiment, a “high IPA PET is used as apolyester based material or major resin which is coated with apoly(hydroxy acid) polymer. As it is used herein, the term “high-IPA PETrefers to PET to which IPA was added during to manufacture to form acopolymer in which the IPA content is more than about 2% by weight,preferably 2-10% IPA by weight, more preferably 3-8%, most preferablyabout 4-5% IPA by weight. As used herein, “PET includes “high IPA PET.”High-IPA PET (more than about 2% by weight) may be preferred becauseimproved interlayer adhesion is obtained.

In other embodiments the poly(hydroxy acid) polymer is used as acomponent of a barrier material that may be blended with recycled orvirgin resin (e.g., PET) to provide barrier properties. Preferredbarrier materials include Copolyester Barrier Materials and Phenoxy-typeThermoplastics. Other preferred barrier materials include polyimidebarrier materials such as Nylon MXD-6 from Mitsubishi Gas Chemical(Japan), “Polyamide Blends” including those polyamides containing PET orother polyesters, whether such polyester was included by blending,compounding or reacting. Other barrier materials having similarproperties may be used in lieu of these barrier materials. For example,the barrier material may take the form of other thermoplastic polymers,such as acrylic resins including poly(acrylonitrile) polymers,acrylonitrile styrene copolymers, polyamides, polyethylene naphthalate(PEN), PEN copolymers, and PET/PEN blends.

Asymmetric (anisotropic) membranes contain a number of layers, each withdifferent structures, permeability's and gas barrier properties. Atypical anisotropic membrane has a surface layer (i.e. the “skin”)supported on a much thicker substructure. The gas barrier properties andpermeation rates are determined primarily by the surface layer; and thesubstructure functions as mechanical support. The graded nature ofasymmetric membranes results in a sidedness to the membrane, requiringknowledge of the upstream side of the membrane for optimal performance.The present invention includes membranes both with and without thisso-called sidedness. Symmetric membranes and/or layers do not have thissidedness.

“Polymers” useful in preparing the membranes or layers (and associatedformed articles such as bottles) of the invention include, but are notlimited to, aromatic polyamides, aliphatic polyamides, celluloseacetates, cellulose nitrate, cellulosic derivatives, ethyl cellulose,polyesters, polycarbonates, copolycarbonate esters, polyethers,polyetherketones, polyetherimides, polyethersulfones, polyetheresters,polysulfones, polyvinylidene fluoride, polybenzimidazoles,polybenzoxazoles, polyacrylonitrile, polyazoaroaromatics,poly(2,6-dimethylphenylene oxide), polyphenylene oxides, polyureas,polyurethanes, polyhydrazides, polyazomethines, polyacetals,styrene-acrylonitrile copolymers, brominated poly(xylene oxide),sulfonated poly(xylylene oxide), polyquinoxaline, polyamide imides,polyamide esters, polysiloxanes, polyacetylenes such aspoly(trimethylsilylpropyne), polyphosphazenes, polyolefines such aspolyethylene, polypropylene and poly(4-methylpentene), polyphenylenes,polyimides, polyesters and so called ladder polymers, polyacrlonitrile,polyphthalamides, polysulfonamides, polyamide-imides, phenylene diaminessuch as ortho-phenylenediamine and meta-phenylenediamine, Matrimid®,Leming P84, polyamide hydrazide, Nylon 6, poly(ethylene-eo-vinylalcohol), polytetrafluoroethylene, and the like and any blends,copolymers, and substituted polymers thereof. Polymers preferred forpreparing the membranes of the invention includeindustrially-practicable polymers such as cellulose acetates.

The thickness of the base support may be between about 75 and about 500microns thick, although other thicknesses may be used such as 100-400microns or 200-300 microns. The polymeric porous base support may bereinforced by backing with a fabric or a nonwoven web material.Non-limiting examples include films, sheets, and nets such as a nonwovenpolyester cloth. The polymer of the porous base support may permeatethrough the pores, be attached on both sides of the support, or beattached substantially on one side of the support.

A layer containing the poly(hydroxy acid) polymer may comprise a singlematerial, a mix or blend of materials (heterogeneous or homogeneous aninterwoven matrix of two or more materials, or a plurality ofmicrolayers (lamellae) comprised of at least two different materials.

In another preferred embodiment, a container is produced having apolymer composition comprising a polyethylene terephthalate (PET)polymer or copolymer, and the poly(hydroxy acid) polymer or copolymer ofthis invention wherein the PET has an intrinsic viscosity between about0.65 and about 1.30 dL/g, and wherein the container is selected from thegroup consisting of an injection molded container, a stretch blow moldedcontainer, an extrusion blow molded container, and a thermoformedcontainer. It is also preferred that in this container, the poly(hydroxyacid) polymer component of this invention is confined to one or morediscrete or semi-discrete layers which have an overall multi-layercontainer structure and that the container is fully compatible with theexisting PET recycling streams as defined by the Association of PlasticsRecyclers (APR) Critical Guidance.

The presence of additives and catalysts during the process of making thethermoplastic polymer may lead to the formation of a product in whichresidues of additives present during the polycondensing, solid-statepolymerizing and/or extrusion reaction remain in the thermoplasticpolymer. These additives may include, for example, catalysts, catalystdeactivators, heavy metal deactivators, heat stabilizers and/orantioxidants. Heat stabilizers and antioxidants, when present, are inamounts of 10 ppm-1%, preferably 100 ppm-0.1%, 50-250 ppm or about 500ppm based on the total weight of the thermoplastic polymer. Residuesfrom catalyst deactivators and heavy-metal deactivators, when present,are typically in lower amounts, e.g., 10-100 ppm, preferably 25-75 ppmor about 50 ppm by weight.

Catalyst deactivators include compounds that have a polar group orfunctionality containing an oxygen, nitrogen, phosphorus and/or sulfuratom, particularly compounds that are acidic (e.g., protic) such asamines, alkali or alkaline earth metal salts of carboxylic acid, water,hydrotalcites. Examples include phosphoric acid, monochloroacetic acid,dodecylbenzenesulfonic acid, p-toluenesulfonic acid, benzoyl chloride,etc. Other deactivators include thioether compounds, vitamin compounds,triazole compounds, polyamine compounds, compounds of hydrazinederivatives, and phosphorous compounds, such as phosphate compounds,phosphite compounds, or metal phosphate inorganic compounds. Specificexamples of the catalyst deactivator include phosphite compounds such as“ADK STAB” AX-71 (dioctadecyl phosphate), PEP-8(distearylpentaerythritol diphosphite), and PEP-36 (cyclicneopentatetraylbis(2,6-t-butyl-4-methylphenyl)phosphite)) available fromADEKA CORPORATION, and metal phosphate inorganic compounds selected fromsodium dihydrogen phosphate, potassium dihydrogen phosphate, lithiumdihydrogen phosphate, calcium dihydrogen phosphate, di sodium hydrogenphosphate, dipotassium hydrogen phosphate, calcium hydrogen phosphate,sodium hydrogen phosphite, potassium hypophosphite, calcium hydrogenphosphite, sodium hypophosphite, potassium hypophosphite, and calciumhypophosphite.

Thermal stabilizer additives include organophosphites (e.g. triphenylphosphite, tris-(2,6-dimethylphenyl)phosphite, tris-(mixed mono- anddi-nonylphenyl)phosphite or the like), phosphonates (e.g.,dimethylbenzene phosphonate or the like), phosphates (e.g., trimethylphosphate, or the like), tris(2,4-di-t-butylphenyl) phosphate availableas IRGAPHOS 168 or combinations.

Antioxidant additives include organophosphites such as tris(nonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite,bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, distearylpentaerythritol diphosphite; alkylated monophenols or polyphenols;alkylated reaction products of polyphenols with dienes, such astetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane;butylated reaction products of para-cresol or dicyclopentadiene;alkylated hydroquinones; hydroxylated thiodiphenyl ethers;alkylidene-bisphenols; benzyl compounds; esters ofbeta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid with monohydricor polyhydric alcohols; esters ofbeta-(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acid withmonohydric or polyhydric alcohols; esters of thioalkyl or thioarylcompounds such as distearylthiopropionate, dilaurylthiopropionate,ditridecylthiodipropionate,octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;amides of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid, orcombinations comprising at least one of the foregoing antioxidants.

A further preferred embodiment is a polymer film or film-derived packagehaving a polymer composition comprising a thermoplastic polymer orcopolymer and the (poly)hydroxy acid polymer or copolymer of thisinvention where the poly(hydroxy acid) polymer component is confined toone or more discrete or semi-discrete layers which comprise an overallmulti-layer film structure, and is also fully compatible with one ormore of the existing recycling streams as defined by the Association ofPlastics Recyclers (APR) Critical Guidance.

Commonly used rigid packages are containers for carbonated andnon-carbonated beverages and food as well as non-food liquids, such asshampoos and household detergents. These containers can be made by atwo-step process. In the first step a preform is produced by injectionmolding, and in the next step the preform is reheated and biaxiallystretched and blown to give final container shape, size, and integritywith desirable thermo-mechanical properties.

Embodiments of the invention include processes of forming a containerusing a thermoplastic polymer according go the present disclosure.Preferably as a pre-conditioning step prior to the injection moldingprocess, the thermoplastic and polyester resin(s) of similar species orphysical mixtures are dried and fed to an injection molding machine froma drying hopper. They are then conveyed and melted by extrusion screwand injected under pressure into a mold. The mold may have one or morepreform cavities to make a one or several preforms in a single cycle.The molded preform may have a single- or multi-layer structure type.

In a multi-layer application, the thermoplastic polymer and one or moredifferent resins may be fed independent of each other to create amultilayered preform structure. For example, a three layer bottle mayhave an AB or ABA structure, where a middle layer of resin B issandwiched between two structural layers of resin A on either side. TheB layer, preferably the layer comprising the thermoplastic polymer, isoften a thin section of the wall, generally about 5-15% of the totalpreform wall thickness. The multi-layer bottles allow for a specializedresin such as the thermoplastic polymer of the present disclosure to beisolated in a specific location within the container. The finalstructure is preferably ABA, the co-injection injection molding sequencemay be A, B; A, B, A; or ABA, A: where A is injected first, while A isbeing injected, B is introduced, then B is stopped and A continues untilthe final preform is packed out.

The timing sequence and mold temperatures can be adjusted to positionthe B layer (e.g., the layer containing the thermoplastic polymer) inthe center of the preform or preferentially to the inside or outside ofthe preform wall. The sequence can also be managed to position thespecialize B layer so that it only falls within the amorphous regions ofthe preforms that will eventually reheated and stretch blow molded. Theadvantage of this is to minimize or eliminate the thermoplastic polymerfrom being in the thicker amorphous regions of the thread finish andbase pushup regions that do not get stretched during a subsequentblowing process. This also allows for the total encapsulation of thethermoplastic polymer. Another option is to create a 5 layer structureABABA via a sequential injection molding sequence A-B-A. In this case, Ais injected first, and then stopped, B is injected next and thenstopped, and then A is injected last packing out the preform. Thiscreates two thin B layers due to the ‘Fountain Flow” filling ofinjection molding cavities.

Conventionally, a resin preform is transformed to a bottle or acontainer by blow-molding. Blow molding, also known as blow forming, isa manufacturing process by which hollow plastic parts are formed. It isa process used to produce hollow objects from thermoplastic. In general,there are three main types of blow molding: extrusion blow molding,injection blow molding, and stretch blow molding. The blow moldingprocess begins with melting down the plastic and forming it into aparison or preform. The parison is a tube-like piece of plastic with ahole in one end in which compressed air can pass through.

The basic process has two fundamental phases. First, a preform (orparison) of hot plastic resin, often in a somewhat tubular shape, iscreated. Second, a pressurized gas, usually air, is used to expand thehot preform and press it against a mold cavity. The pressure is helduntil the plastic cools. This action identifies another common featureof blow molded articles. Part dimensional detail is better controlled onthe outside than on the inside, where material wall thickness can alterthe internal shape. Once the plastic has cooled and hardened the moldopens up and the part is ejected.

In the blow molding step, preforms are loaded on a conveyor andpreferably passed in front of infrared (IR) heating lamps to heat thepreform typically 10-20° C. above the polymer glass transitiontemperature (T_(g)) prior to one or more the stretching and/or blowingsteps. The preform s thicker and shorter than the final container wallto account for the self-leveling of the polymer and the resulting axialand hoop stretch ratios (blow up ratio BUR) of the final containershape. To reheat the preform uniformly, typically, a low concentrationof IR absorbing species, called reheat or fast heat up additive, areadded to one or more layers, preferably PET layers, to improve theabsorption of IR-radiation by the polyester preform and subsequentlyconduct heat into the surrounding preform wall section.

The thermoplastic polymer of the present disclosure can be processed byany method of processing a resin, e.g., by melting the polymer, forminga shaped article from the molten polymer, and cooling the shaped articleto form a solid shaped article. Processing includes any method by whichthe thermoplastic polymer is transformed from a solid form to a flowableand/or plastic form. The transforming may include heating thethermoplastic polymer beyond the glass transition temperature thenforming a shaped solid article from the heated thermoplastic polymer.Processing further includes any method by which a solid thermoplasticpolymer and/or co-resin such as a PET resin is heated above its glasstransition temperature and/or melt temperature and is subsequentlyand/or concurrently formed into a shaped article, including: injectionmolding, reaction injection molding (RIM), stretch blow molding,injection blow molding, recycling, extrusion molding (including EBM),compression molding, thermoforming, and such methods for processingpolyester resins as described in “PET Packaging Technology,” by David W.Brooks and Geoff Giles (2002), the portions of which describe processingmethods for polyester resins and/or PET resins are incorporated hereinby reference. Preferred processing for forming a container or filmincludes injection (blow) molding, sheet and film extrusion, profileextrusion, extrusion blow molding (EBM) and compression molding; mostpreferably EBM.

The IV of the polyester resin that may be used in the method of theinvention to form one or more layers separate from or in combinationwith the thermoplastic polymer may fall within a wide range. Forexample, the IV of the polyester resin may be from 0.6 to 1.0 dL/g,preferably from 0.65 to 0.9, more preferably from 0.7 to 0.85, even morepreferably from 0.72 to 0.80, especially preferably about 0.76.

The extrusion blow molding (EBM) process is the most common process forproducing containers such as plastic bottles, particularly large plasticbottles. The basic extrusion blow molding process comprises plasticizingor melting the thermoplastic polymer and/or a resin in an extruder,forming a parison by extrusion of the molten resin through a die into amold, blowing the parison to fit the shape of the bottle mold andcooling, then deflashing of the blown bottle and ejection of thefinished product. Variations can include multiple extruders forcoextrusion of two or more materials for multilayer bottle structures,parison programmer to shape the parison to match complex blown productshapes and wall thickness, and multiple mold clamp systems to improveoutput through the use of multiple molds.

In the EBM process, an extruder melts, mixes, and feeds a homogeneousmolten polymer into a die head that forms the molten hollow plastictube, called a parison, used in blowing hollow containers or otherhollow products. The first step is extrusion of a hollow plastic parisonwhich is usually in a downward direction for making bottles. Next, thetwo halves of the mold close on the parison, capturing it as it is cutoff from the extruder by a cold or heated cut-off knife. A blow pin or aneedle is inserted and air is blown into the mold, expanding theparison. In some cases the blown pin cooled by water, assists in formingthe thread finish by compressing the thread finish section into the mold(neck calibration), rather than simply blowing it in. This results in asmooth interior in the finish region. In the needle blow case, theneedle is inserted into a part of the molded object that is trimmed offforming the final container shape, and the inside of the finish isformed only by air. The mold is cooled, usually with water, to solidifythe plastic. When the container is cool enough to maintain its shape, itis ejected from the mold.

The extrusion of the thermoplastic polymer to form the multi-layer EBMparison may be carried out under different conditions. Preferably,extrusion is carried out with an EBM apparatus that is capable ofcompletely melting the thermoplastic polymer and any correspondingpolyester co-resin and having sufficient injection pressure to rapidlyextrude the molten resin through a shaped die into the desired parisonshape. The extruder portion of such a molding apparatus may contain aplurality of heating zones. The temperature of each heating zone isindependently controlled. The number of heating zones is not limited,preferably, the number of heating zones is 4 or more, more preferably 5or more, more preferably 6 or more, more preferably 7 or more, morepreferably 8 or more, even more preferably 9 or more, most preferably 10or more. Each heating zone is capable of heating the polyester resin toa temperature above the melting temperature of the polyester resin. Thetemperature of any zone may vary from, for example, 400 to 600° F.,preferably from 450 to 550° F., more preferably from 475 to 525° F.,most preferably about 500° F. Any of the aforementioned temperatures maybe varied by any increment of, for example, 2, 4, 6, 8 or 10° F., or anymultiple thereof.

The screw speed of an EBM apparatus used to carry out the molding may bevaried as needed to adjust cycle time and other factors of the extrusionprocess. For example, the screw speed may be from 5 to 100 rpm,preferably from 10 to 80 rpm, more preferably from 20 to 60 rpm, morepreferably from 30 to 50 rpm, more preferably about 40 rpm. The screwspeed may be varied in any increment of 1, 2, 4, 6, 8 and 10 rpm withinany of the aforementioned ranges, or any multiple thereof.

The head pressure of the extrusion process may be varied and may rangefrom 0 to 1800 psig, preferably from 300 to 1500 psi, more preferablyfrom 800 to 1200 psi. The cycle time is preferably less than 30 seconds,more preferably less than 20 seconds, and most preferably less than 10seconds. The cycle time is the total time from clamp open to clamp open.The cycle time is usually defined by the following functions; moldclose, blow air injection, hot-knife cut, mold shuttle, part cooling,mold open, part ejection, mold return, mold close. Simultaneously andwithin the same amount of time, resin is being melted into a liquefiedstate, the resin is undergoing conditioning (e.g. extrusion), and themolten resin (e.g., polymer melt) is continuously forming anotherparison in preparation for transfer into the mold space. One methodincludes feeding the resin into an extruder for melting and mixingwithin a heated extruder with a revolving screw that compresses andconditions the polymer as it changes phase from a solid to a liquid, theliquefied resin is then continuously extruded into a hollow parisonwhich is subsequently captured into a mold. Since these actions maydependently coincide, a correlation can be drawn between the time of thecycle, and the time that the polymer is in the liquid phase. Thiscorrelation may differ from bottle parison to bottle parison and frommold to mold and from machine to machine.

The flash is trimmed from the container neck and bottom, as well as fromother areas that are pinched off, for instance to form handles or offsetnecks. The mark left from the removal of the flash serve as an easymeans for identification of extrusion blow-molded containers. Usually,this is easiest to see on the bottom of the container. It typicallyappears as a rough area along the mold parting line, centered in themiddle of the bottom and running half or so of the distance to the heelof the bottle. It is also possible, on careful examination, to identifythe roughness at the top of the finish, or on other areas where flashwas trimmed.

During molding the bottle from the hot, molten/softened parisonfollowing capture into the mold, the parison is expanded under pressureby a gas to fill the outer dimensions of the mold. During this blowingprocess the thermoplastic polymer and/or polyester resin may undergosignificant stretching. Typically in EBM there is little or no axialstretch since the extruded parison is longer than the length of the moldin order to insure top and bottom capture into the mold. The hoopstretch ratio of the EBM container may be, for example, from 3 to 7times, preferably from 3.5 to 6.5 times, more preferably from 4 to 6times, most preferably from about 4.5 to about 5.5 times, even morepreferably about 5 times.

The bottle parison may then be blown into a straight wall mold or intoshaped and/textured molds and of all sizes may be used withoutrestriction. One handleware bottle form is a two-liter or larger laundrydetergent bottle. Another form is a one-gallon juice bottle.

EXAMPLES

¹³C NMR spectra were acquired at 22° C. on a 600 MHz Bruker Avance IIINMR spectrometer equipped with a QCI (H—P/C/N-D) cryoprobe. An inversegated pulse sequence with 30 degrees flip angle was used and 4096 scanswith 16 dummy scans were collected. The acquisition time was 0.9 s andthe relaxation delay was 3 s. Samples were dissolved in a 2:1 v/vmixture of 1,1,3,3,3-hexafluoro-2-propanol (99.9%, Fluorochem) anddeuterated chloroform (99.8%, VWR). Chromium (III) acetylacetonate (97%,Aldrich) was added as a relaxation agent. The quantitative ¹³C NMRspectra were used for the end group analysis and the calculation ofaverage number molecular weights (M_(a)) according to a protocoldeveloped earlier at VTT

Molecular weight and molecular weight distributions of PGA polymers weredetermined by Size Exclusion (Gel Permeation) Chromatography at 40° C.The measurement system was equipped with Waters Styragel columns andWaters 2410 refractive index detector. The eluent used was Fluorochem1,1,3,3,3-hexafluoro-2-propanol (99.9%) with Sigma-Aldrich 5 mM sodiumtrifluoroacetate (98%) delivered at a rate of 0.5 mL/minute. The resultswere calibrated against poly(methyl methacrylate) standards from AgilentTechnologies.

Differential scanning calorimetry (DSC) measurements were performed onDSC2 equipment (Mettler Toledo GmbH, Switzerland). Samples were heatedfrom 0 to 240° C. at the dynamic heating rate of 10° C./min. The programconsisted of the following segments: 1) dynamic phase from 0° C. to 110°C.; 2) isothermal phase at 110° C., 60 min.; 3) dynamic phase from 110°C. to 240° C. (first heating); 4) isothermal phase at 240° C., 10 min.;5) dynamic phase from 240° C. to 0° C. (first cooling); 6) isothermalphase at 0° C., 2 minutes; 7) dynamic phase from 0° C. to 240° C.(second heating), 8) isothermal phase at 240° C., 2 minutes; and 9)dynamic phase from 240° C. to 20° C. (second cooling). Glass transitiontemperatures (T_(g)) were determined from the second heating scan. Themelting temperature (T_(m)) and crystallization temperature (T_(a)) wereevaluated from both heating and cooling steps.

By utilizing this process, recipe, and their preferred embodiments, asdescribed herein, PGA pre-polymer, intermediate polymer and finalpolymer suitable for co-injection molding or co-extrusion blow moldingwith PET may be produced.

Tables 1 and 2 describe two series of pre-polymers formed bypolycondensing glycolic acid in two different type reactors. Table 3describes the results of chain extension in which a solid reactionmixture that contains a BOX coupling agent and a poly(hydroxy acid)prepolymer is subject to extrusion and mixing in a twin screw extruderand the properties of the corresponding poly(glycolic acid) polymers.Irganox B215 and BASF PEP-36 are examples of commercially availablethermo-oxidative stabilizers that were evaluated.

TABLE 1 Characterization of carboxylic chain-end terminated PGAintermediate prepolymers prepared from technical grade glycolic acid ina Drais type reactor. Glycolic Adipic Trimellitic Methoxyacetic MeltMelt Sample Catalyst Stabilizer Acid Acid Anhydride Acid Temp Time Code(wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (° C.) (hrs) PGA Drais 4.20.05 0.1 97.65 1.90 0.00 0.3 200 7 PGA Drais 5.2 0.03 0.1 97.37 0.951.25 0.3 200 7 PGA Drais 6.2 0.03 0.1 97.42 1.90 0.25 0.3 200 7 PGADrais 7.2 0.03 0.1 98.25 0.95 0.375 0.3 200 7 PGA Drais 8.2 0.03 0.297.38 1.90 0.1875 0.3 200 7 PGA Drais 9.2 0.03 0.2 98.25 1.425 0 0.1 2007 PGA Drais 12.2 0.03 0.2 97.20 1.90 0.375 0.3 200 7 PGA Drais 13.2 0.010.2 97.22 1.90 0.375 0.3 200 7 PGA Drais 14.2 0.02 0.2 97.21 1.90 0.3750.3 200 7 PGA Drais 15.2 0.02 0.2 97.46 1.52 0.50 0.3 200 7 PGA Drais16.2 0.025 0.2 97.46 1.52 0.50 0.3 200 7 PGA Drais 17.2 0.03 0.2 96.692.28 0.50 0.3 200 7 PGA Drais 18.2 0.03 0.2 96.95 1.90 0.625 0.3 200 7PGA Drais 19.2 0.06 0.4 96.72 1.90 0.625 0.3 200 7 SSP SSP NMR SampleTemp Time COOH—COOH M_(n) GPC (g/mole) Code (° C.) (hrs) (%) (g/mole)M_(n) M_(w) M_(p) PDI PGA Drais 4.2 175 48 86 3,050 10,910 23,820 24,6302.18 PGA Drais 5.2 170 48 73 3,760 13,560 24,640 26,230 1.8 PGA Drais6.2 160 40 93 2,980 11,910 25,650 28,540 2.15 PGA Drais 7.2 160 48 764,380 20,680 34,610 33,210 1.67 PGA Drais 8.2 160 44 97 3,300 — 24,850 —— PGA Drais 9.2 160 44 92 3,850 — 27,120 — — PGA Drais 12.2 150 72 963,000 — 29,310 — — PGA Drais 13.2 160 48 92 2,930 — 25,730 — — PGA Drais14.2 160 48 93 3,100 — 29,765 — — PGA Drais 15.2 158 68 88 3,800 —36,060 — — PGA Drais 16.2 159 55 92 3,240 — 27,800 — — PGA Drais 17.2159 51 91 2,530 — 20,165 — — PGA Drais 18.2 159.5 53 94 2,900 — 25,430 —— PGA Drais 19.2 159.5 53 97 3,170 — 22,315 — —

The examples presented in Table 1 demonstrate a portion of the widevariety of compositions and polycondensation process conditions whichwere considered and attempted in a Drais type reactor for preparing thepoly(hydroxy acid) intermediate prepolymer of the present disclosure.Some attributes of these examples led to the preferred embodiments notedin the description and claims of the present disclosure. These resultsalso led to additional series of experiments that were carried out in alarger Lodige type reactor.

TABLE 2 Characterization of carboxylic chain-end terminated PGAintermediate prepolymers prepared from technical grade glycolic acid ina Lodige type reactor. Glycolic Adipic Trimellitic Methoxyacetic MeltMelt Sample Catalyst Stabilizer Acid Acid Anhydride Acid Temp Time Code(wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (° C.) (hrs) PGA 0.06 0.4 96.71.90 0.625 0.3 200 7 Lodige 1.2 PGA 0.06 0.4 96.7 1.90 0.625 0.3 200 7Lodige 2.2 PGA 0.06 0.1 97.0 1.90 0.625 0.3 200 7 Lodige 3.2 PGA 0.060.1 97.0 1.90 0.625 0.3 200 7 Lodige 4.2 PGA 0.06 0.1 97.0 1.90 0.6250.3 200 7 Lodige 5.2 PGA 0.06 0.6 97.0 1.425 0.625 0.3 200 7 Lodige 6.2PGA 0.06 0.7 97.1 1.33 0.50 0.3 200 7 Lodige 7.2 SSP SSP NMR Sample TempTime COOH—COOH M_(n) GPC (g/mole) Code (° C.) (hrs) (%) (g/mole) M_(n)M_(w) M_(p) PDI PGA 160 53 94 3,010 — 24,380 — — Lodige 1.2 PGA 160 5396 3,160 — 27,060 — — Lodige 2.2 PGA 160 53 97 3,140 — 21,720 — — Lodige3.2 PGA No No 80 2,170 — 17,150 — — Lodige 4.2 SSP SSP PGA 160 53 952,980 — 19,770 — — Lodige 5.2 PGA 165 53 95 4,000 8,320 26,150 29,8703.14 Lodige 6.2 PGA 165 68 95 4,280 14,386 30,614 31,890 2.13 Lodige 7.2

Similarly, the examples presented in Table 2 demonstrate the breadth andvariety of compositions and polycondensation process conditions thatwere considered and attempted in a larger Lodige type reactor forpreparing the poly(hydroxy acid) inter mediate prepolymer of the presentdisclosure. Some attributes of these examples led to the preferredembodiments noted in the description and claims of the presentinvention. These preferred samples were used to develop the preferredembodiments of the reactive extrusion process as well as the preferredembodiments and compositional claims of the final poly(hydroxy acid)polymer which is one of the overall objective of this disclosure.

TABLE 3 Chain extension experiments performed with a twin-screw extruder(TSE) and molar masses and molar mass distribution of TSE chain-extendedPGA polymers with their corresponding intermediate prepolymers. TSE TSEMelt Die Sample Intermediate BOX Stabilizer Speed Torque Temp PressureGPC (g/mole) Code Prepolymer (wt %) (wt %) RPM (%) (° C.) (Bar) M_(n)M_(w) M_(p) PDI TSE-618 PGA Drais 6.2 5.00 0.40 240 N/A N/A N/A 29,56084,150 67,270 2.85 TSE-749 PGA-Drais 4.2 3.00 0.20 180 N/A N/A N/A33,780 95,950 75,770 2.84 TSE-765 PGA-Drais 4.2 + 3.25 0.20 180 N/A N/AN/A 27,870 89,880 71,050 3.22 PGA-Drais 7.2 TSE-71 PGA-Drais 4.2 + 5.000.30 150 N/A N/A N/A 29,740 102,840 69,500 3.45 PGA-Drais 5.2TSE-L646-0-0-0 PGA-Lodige 6.2 4.60 0.80 180 77 245 63-64 25,890 120,42067,430 4.65 (Sample A) TSE-L646-0-0-0 PGA-Lodige 6.2 4.60 0.80 180 77245 63-64 26,320 113,470 65,380 4.31 (Sample B) TSE-L6475-0-S PGA-Lodige6.2 4.75 0.80 180 70-85 243 65-80 29,110 148,730 69,020 5.11 (Bag 1)TSE-L6475-0-S PGA-Lodige 6.2 4.75 0.80 180 70-80 243 100-150 32,230154,860 71,210 4.80 (Bag 4) TSE-L6475-AX-S PGA-Lodige 6.2 4.75 1.00 18065-85 243  90-115 24,690 134,960 63,890 5.47 (Bag 2) TSE-L649-0-0-SPGA-Lodige 6.2 4.90 0.80 180 76 244 100-120 23,210 126,680 61,970 5.46TSE-L7395-0-S-B PGA-Lodige 7.2 3.95 0.70 190 68-80 242 105-125 27,560130,230 70,110 4.73 TSE-L7395-AX-S PGA-Lodige 7.2 3.95 1.10 190 63-67242 100-150 24,690 134,960 63,890 5.47 (Bag 2) TSE-L740-AX-S-BPGA-Lodige 7.2 4.00 0.90 190 66 243 95 28,950 141,240 65,380 4.88TSE-L740-AX-S PGA-Lodige 7.2 4.00 1.10 190 67 243 110-140 28,310 131,71062,450 4.65 (Bag 1) TSE-L740-AX-S PGA-Lodige 7.2 4.00 1.10 190 65 243110-130 24,580 118,730 61,040 4.83 (Bag 3) TSE-L740-0-0-S PGA-Lodige 7.24.00 0.90 180 80-90 245  95-110 27,380 138,980 69,560 5.08

The examples presented in Table 3 demonstrate the variety of recipes andreactive extrusion process conditions that are included in the presentdisclosure and were considered and attempted during development of thepreferred embodiments of the present poly(hydroxy acid) final polymer.In particular, examples using the Lodige 7.2 intermediate prepolymerwith lower Brancher and BOX levels compared favorable to examples usingthe Lodige 6.2 intermediate prepolymer with higher Brancher and BOXlevels, specifically with respect to the final polymer viscositystability over extended time in the melt phase.

TABLE 4 Comparative examples of linear and branched PGA polymers withdifferent amounts of a chain-terminating ingredient. AdipicMethoxyacetic Trimellitic Die Sample Intermediate Acid Stabilizer AcidAnhydride BOX Pressure Code Prepolymer (wt %) (wt %) (wt %) (wt %) (wt%) (Bar) TSE- PGA Drais 1.425 0.40 0.1 0 3.60 N/A 9036(a) 9.2 TSE- PGADrais 1.425 0.40 0.1 0 3.60 N/A 9036(b) 9.2 TSE- PGA Drais 1.90 0.30 0.30.25 4.50 N/A 6045 6.2 TSE- PGA Lodige 1.33 1.10 0.3 0.50 3.95 100-1507395- 7.2 AX-S TSE TSE Melt Sample Speed Torque Temp GPC (g/mole) CodeRPM (%) (° C.) M_(n) M_(w) M_(p) PDI TSE- 240 N/A 233-250 21-25,00068-77,000 — 2.85-3.43 9036(a) TSE- 240 N/A 233-250 21-25,000 68-77,000 —2.85-3.43 9036(b) TSE- 270 N/A 229-239 21-27,000 64-94,000 — 3.05-3.726045 TSE- 190 63-67 242 24,690 134,960 63,890 5.47 7395- AX-S

Table 4 presents comparative examples of linear versus branchedpoly(hydroxy acid) final polymers with differing levels of (1) brancher,as trimellitic anhydride, and (2) chain terminator, as methoxyaceticacid. These examples demonstrate the preferred embodiment of the presentdisclosure wherein the branched polymer has the ability duringpolycondensation to incorporate and render harmless (e.g., inactivate orscavenge the terminator function of the chain-terminating impuritypresent in the monomer feedstock) the undesired chain-terminator. Achain terminator that has been rendered harmless is no longer effectivein inhibiting the polymer chain growth, intermediate and final molecularweight, and/or melt viscosity of the final poly(hydroxy acid) polymer.

TABLE 5 Comparative examples of the capillary melt viscosity for linearand branched PGA polymers. Sample Code: TSE-9036(a) TSE-9036(b) TSE-6045TSE-7395-AX-S Intermediate Prepolymer Drais 9.2 Drais 9.2 Drais 6.2Lodige 7.2 Cap Visc Temp (° C.) 230 230 230 230 Shear Rate (1/s)Capillary Shear Viscosity (Pa-s) 27.5 137.7 270.6 471.1 1510 50 122.1164.6 384.9 1072 91.3 99.0 120.8 323.8 774.8 166 89.6 97.2 267.6 558.6302 83.8 87.3 218.3 407.2 550 75.1 75.7 174.6 295.4 1002 66.7 66.8 137.3208.3 1824 56.6 57.2 106.8 150.3 3321 46.5 46.8 81.3 108.4 5497 37.937.7 61.7 80.7

Table 5 and FIG. 3 demonstrate an embodiment by comparing thesubstantially lower melt viscosity after reactive extrusion which wasachieved with TSE-9036, a linear poly(hydroxy acid) final polymer, ascompared with TSE-6045, a branched poly(hydroxy acid) final polymer.Clearly, the presence of the active chain terminator in TSE-9036 loweredavailable reactive sites, final molecular weight, and the capillary meltviscosity of this linear example versus the harmlessly incorporatedchain terminator within the branched structure of the TSE-6045 polymerof the comparative examples.

In addition, Table 5 and FIG. 4 demonstrate that within the family ofbranched polymers, it is observed that the intermediate prepolymerrecipe, the polycondensation process conditions, and the reactiveextrusion recipe and process may all contribute to a preferredembodiment as demonstrated by higher capillary melt viscosity of thefinal poly(hydroxy acid) polymer.

As another embodiment of the invention, it was observed that there arepreferred levels of linear polycondensation initiator, branchedpolycondensation initiator, and reactive extrusion chain-extender whichresult in good downstream processing (e.g. injection molding,stretch-blow molding, film casting, thermoforming, etc.) of thepoly(hydroxy acid) polymer and good container performance (e.g. smallCSD bottles, large EBM juice bottles, flexible film packaging for snackfoods, etc.)

A key observation related to suitability for downstream processing isthe “long-term” thermal stability of the final poly(hydroxy acid)polymer. In this context long-term stability is the stability of themelt viscosity (or representative force measurement) at temperatureabove the poly(hydroxy acid) polymer melt point for times ranging frommore than 1 minute up to 20-30 minutes. Excessive levels of branchedinitiator, such as TMA, and/or chain-extender, such as BOX, can have anegative effect on the final polymer viscosity and hence, on its abilityto be successfully processed into desirable articles for packaging.

FIG. 5 displays a scan of melt force (surrogate for melt viscosity)versus time for four final polymer recipes made from the same Lodige 7.2intermediate prepolymer. These four different final polymers were nearlyidentical except that they were reactively extruded with four differentlevels of BOX chain extender. PGA samples L738-0-0-S, L739-0-0-S,L740-0-0-S, and L741-0-0-S were extruded with 3.8 wt. %, 3.9 wt. %, 4.0wt. %, and 4.1 wt. % BOX, respectively. As FIG. 5 demonstrates, finalpolymer melt viscosity behavior/stability between approximately 2-10minutes is impacted significantly by the increasing BOX level used toproduce the different polymers. Since a time-stable (flat) meltviscosity (force) curve is desired for downstream processing, it isclear that too much or too little chain-extender can negatively impactbehavior of the final poly(hydroxy acid) polymer. Too much chainextender is understood to de-stabilize final polymer melt viscosity overtime while too little chain extender is understood to decrease finalpolymer melt viscosity below the threshold for satisfactory downstreammelt processing performance.

FIG. 6 demonstrates that the level of branched polycondensationinitiator in the intermediate prepolymer can influence the long-termmelt viscosity behavior of the final poly(hydroxy acid) polymer evenmore dramatically than the level of chain extender used for reactiveextrusion. The upper four, highly unstable melt viscosity (force) curveswere generated using poly(hydroxy acid) polymers produced from Lodige6.2 intermediate prepolymer. By comparison, the lowest, stable meltviscosity (force) curve was generated using final poly(hydroxy acid)polymer produced from Lodige 7.2 intermediate prepolymer. In addition tothe higher BOX levels (from 4.75% to 5.1%) of the four upper curves ascompared with the lowest curve (3.9%), Lodige 6.2 intermediateprepolymer was produced with 25% more branched initiator as comparedwith Lodige 7.2 (0.625 versus 0.50 wt. %).

The additional, excessive branched polycondensation initiator appearsresponsible for the dramatic melt viscosity (force) instability observedbetween approximately 2-10 minutes. Furthermore, the optimum levels ofbranched polycondensation initiator and chain extender necessarilydepend upon the specific levels of chain terminator and linearpolycondensation initiator, since only excessive amounts of branchedinitiator and chain extender would have the highly deleterious effectseen in FIG. 6 .

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

The invention claimed is:
 1. A thermoplastic polymer, comprising reactedunits of: a hydroxy acid compound selected from the group consisting ofglycolic acid, lactic acid, and mixtures thereof, (ii) 0.5-2.5 wt % of adi-functional acid initiator comprising one or more dicarboxylic acidsor a mixture of dicarboxylic acids, (iii) 0.2 to 1 wt % of amulti-functional acid initiator selected from the group consisting oftrimellitic acid, trimellitic anhydride, and mixtures thereof, (iv) from0.15-0.45 wt % of methoxyacetic acid chain-terminator, (v) optionally, areactive chain-extending coupling-agent comprising a bis-oxazoline; andone or more components that may optionally be reacted with thethermoplastic polymer: (vi) optionally, one or more catalysts selectedfrom the group consisting of antimony trioxide, antimony glycolate,camphorsulfonic acid, cobalt acetate, tin (II) chloride, stannousactuate, zinc acetate, zinc lactate, and methanesulfonic acid, and (vii)optionally, an additive package selected from the group consisting of acatalyst deactivator, a heavy-metal deactivator, a heat stabilizer, anantioxidant, and mixtures thereof.
 2. A container having an opening anda cavity defined by a polymer wall, wherein the polymer wall comprises:a polyethylene terephthalate (PET) polymer or copolymer, where the PEThas an intrinsic viscosity between about 0.65 and about 1.30 dL/g, andthe thermoplastic polymer of claim 1, wherein the container is selectedfrom the group consisting of an injection molded container, a stretchblow molded container, an extrusion blow molded container, and athermoformed container.
 3. The container of claim 2, where thethermoplastic polymer is confined to one or more discrete orsemi-discrete layers in a multi-layer container structure.
 4. Thecontainer of claim 2, that meets requirements for recycling defined bythe Association of Plastics Recyclers (APR) Critical Guidance.
 5. Apolymer film or film-derived package having a polymer compositioncomprising the thermoplastic polymer of claim 1 and one or more of asecond thermoplastic polymer or copolymer.
 6. The polymer film orfilm-derived package of claim 5, wherein the second thermoplasticpolymer or copolymer is present in one or more discrete or semi-discretelayers which comprise an overall multi-layer film structure.
 7. Thepolymer film or film-derived package of claim 5, that meets therequirements for recycling defined by the Association of PlasticsRecyclers (APR) Critical Guidance.
 8. The thermoplastic polymer of claim1, comprising the reactive chain-extending coupling-agent in an amountfrom 4.0 to 5.0 wt %.
 9. The thermoplastic polymer of claim 1,comprising glycolic acid in an amount of at least 90% by weight based onthe total weight of the thermoplastic polymer and the thermoplasticpolymer has a weight average molecular weight of greater than 100,000 byGPC.